I think this isn’t quite up to date on the stuff in the meetings as well.
At first glance, we have these:
http://tamriel-rebuilt.org/content/2015-03-07-meeting-summary
http://tamriel-rebuilt.org/content/2015-03-21-meeting-summary
which are already quite extensive and not in the handbook yet.

Have you been looking at the other threads besides the brainstorming one? Reason I ask is there’s a ton of them dotting the old forums, also some mentions buried in threads that aren’t specifically marked for Indoril.

I’m going to throw up a thread whre I’m just looking for references and mentions to ideas for the various factions (and other things). WIP in and of itself. And I’m also writing these summaries under the assumption it’s all suggestions at this point, for us to argue over once we have all the summaries up and running.

Could Sedura make a come back as title as well? IIRC, Sedura is the honorific given to wealthy Dunmer or landowner (or both)

What about the dunmer noble overhaul mod? There are some great pieces in that mod that could also be used for he indoril lords to further set them apart as a different sect of society as well.

The chapels could always be named after the original lords, but yeah, I'm not entreily sold on the idea either. I felt it would be worth sharing, at least.

The Dunmer Nobles Overhaul mod Templar Tribe mention looks interesting. I could see some of hairstyles fitting the Indoril, though some of sort of have a Padme  Amidala vibe to them.
 

Summary of all things we got after conversation with Gnomey in discord about house Indoril.

Buildings and tilesets problems:
Mournhold tileset is awesome looks sometimes, but it hard to work and this set alone far from Tes3 and TR's Morrowind interpritation and mostly look like more modern view on Altmers. This houses maded from stone, metal and a lot high quality windows and stuff, which is very contrasts  with other Dunmer archeticture, which one is mostly made from natural materials and more simple as it is. Also this conflicts with Tribunal Temple opinion on this parts of Dunmer and overall meric culture elements and house Indoril, most close house to the Tribunal Temple should not look like it altmers that yesturday moved here.
Along with that, vanilla mournhold Tielset was maded to play clear role in not very big interior in specific location, and with this hard to make a lot new towns, places, manors etc. because it very limited.

Region and flora/fauna problem:
As all old TR regions, most of already finished MAP3 regions look not very uniqle and not represent any features to great house itself. regions like Lan Otheran looks awesome from clear stylistic part and towns like Bosmora in this region very well pick original Tribunal add-on style and expand it (this was one of reasons I was mostly against of re-do this thing, since it look different than other MW, and same time pretty quality represented). BUT, there always BUT. Trbunal addon itself is pretty generic and actually step back from concept of really interesting and uniqle morrowind - that actually what gams like ESO and TES4 made in future with it. Like currently indoril is: a bunch of generic elf towns in green forests with some random elements from previous parts like stilt-striders and netches and skyrenders. This is way lower than modern TR standarts. Overall, currently House Indoril, which one need to be closest house to Temple is maximum generic elf country. And yep, even if this make it look different from other houses and morrowind communities, it not make it look really uniqle to ba even on main tes3 level.

Proposal and ideas for resolving this problem:
Since Tamriel Rebuild is gonna fully remade Tribunal, there are no problems to reimagine a lot things, trouth, I think we can still use a lot stuff from this. Most inmportant that we can move our imagination far from generic "just forests and just elfs" tier thinking and make Indoril proper uniqle part of wierd Dunmer family. Also update or even create new sets to make it more easy work in future.
Main goals - 1.Make Indoril Towns more dunmeri and follow basic ideas about House in TR lore. 2.Make Indoril lands more interesing place to visit. 3.Make more logic of house role, economy, belives and place in world.

Achetecture ideas:
1.Main preoblem currently, which one need be resolved in near future is Indoril Chapels (because Roa Dyr, you know). At now, main idea use for Indoril Chapels and for Tribunal Temples in Indoril lands style of Mournhold Almalexia Temple. It kinda reminds some old Dunmer styles and look really morrowindy, but same time more exquisitely, what makes this style perfect for Indoril.
Gnomey made simple sketch, which parts of temple design may be used as direct refference for new set of meshes:

Adittionaly, some insperation can be maded from this pices of Old Mournhold meshes because their style not very far:

2.Other set that was disscuesd for a long time is Lower Indoril one. It was very hard question, because overall indoril towns concept it not perfectly clear. Main idea that Indoril should have only Chapels, Estates and Strongholds, and no proper big towns with middle class and all that stuff, exept Akamora  "that lay claim to same land, and so they're sort of keeping each other n check and unable to function properly". But lower class should exist, and there a lot places where it can be used: a).As replace for most of shack tielset use in indoril lands. Shaks are overused in TR and it be logical if Indoril pesants will live in this indoril-style lower buildings. b).Plantations and manufactures - indoril have a lot of pesants, farmers and slaves, this set of archetecture will find good use here. Good example where it can be used - akamora mines c).Towns and places around chapels and some buildings around estates, such as already metioned Roa Dyr. Also to avoid of using Velothi meshes near Indoril buildings, since stylemixing is not very good and vanilla velothi structures not very fit south regions.
Look of that style can be based on other Old Mournhold parts:

This buildings have a lot common with other morrowind and dunmer structures, such as velothi style, hlaalu style, even some telvanni and daedric ruin elements (round doors, materials used, ornamets etc.). There was already some concepts by different people in TR like Gnomey sketches in first post: here, but sadly, photobucket show only preview for me now and this one

So for my sketch of indoril lower class I tried to follow already metioned ideas. Like 1.It need to be in kinda similar style and colors of MH set. 2.It need use more organic materials such as wood and need be more dunmer origin. 3.It need take some ideas from metioned Old Mournhold blocks and expand them to proper building set and what I got:

I used elements from OM set, like round doors and main for of buildings and use of wood. For lighthose I used pillars with ornaments on them from OM part of set that reminds daedric ruins set. But also I tried to make they match with already created indoril style - similar set of colors and roofs will remind some china and japan stuff, but again, they made mostly out of wood, not stone and metal. They also be much more easy to work with and will remind of already existing dunmer styles. More than that, there also was other interesting concept for lower class indoril:

My style of set can be used alongside with this idea of canton-like lower class. Big circular indoril cantons with lower class buildings inside them and regular lower class set on top. It will be very close in spirit to velothi cantons and dres cantons, so it maximum dunmer as you can get. But they should probably be used exlusevly in Mournhold, and there we can ove on next sub-topic

3.Main Tribunal buildings style. All other sets already fill most needs of TR, alongside with limited use of shacks and velothi it cover all need for archetecture of House Indoril. But what with currently used set? Gnomey said that in perfect world TR just delet it and forget, and it fully understandable, however I have a little bit different opinion. Yeah, that set looks generic, not fit lore and logic as main Indoril style, but it already iconic for  lot playesrs, it looks good if you forget about lore and actually it may find limited use where it will look not out of place and will make TR view of House Indoril even more uniqle and interesting. Exept maybe one-two uses around random places on map, it can work in Akamora - this town is pretty unusial location for house, already kinda famous place for players and this will be something fresh for players who tired from other regular indoril settlements. Other use - 'restored' (build anew) lost Chapel of the Garden Id Vano, may be as one option for players to build it in that style if player have acces to a lot of requred materials and don't want build regular chapel. And third and most important - Almalexia.
  This city need be very different from other indoril towns - this is like Port Telvannis for Telvanni house - this is capital, this is only real one city of House Indoril and actual capital of morrowind. Similar like houses in vivec live in indoril cantons, houses here need to live in something builded by indoril for that purpose. As was said before, this city will contain some poor and common districts, filled with circular cantons ad lower indoril sets. Temple district and some parts of city like paza will contain some regular Indoril Chapel style buildings, but mostly city filled with what was in actual tribunal addon, especially Castle ( this will emphasize the difference between the power of the temple and the secular rule of king). Some other high districts like Godsreach. This city build in indoril lands, by indoril, and have a lot indoril parts, but it mostly serve as something different, it was builded to be capital not of indoril, but of all morrowind and as Port Telvannis and houses cantons in vivec different from their main house themes, this city should be different from regular indoril estates. There even can be some dialogue about it with Indoril and temple guys: "At least this is not build by Imperials" 

Old screenshot to show how awesome it was when you first time visit tribunal addon

Regions, flora, fauna and places around indoril lands
Aanthirin clearly show, what means be uniq region by most modern TR standars. It's clear, that a lot old TR lands are far from this requirements and most Indoril lands are not an exception. Better start from major stuff
In my opinion all indoril lands musy be mostly flat. It was in original bethesda morrowind concept map - this lands has no any moutian ranges and was called "central plain". I think it be good follow this idea - at first, TR map is pretty big to have stuff like that, a lot hills and rocks in original bethesda games was maded to hide small size of map. Flat regions is what looks most epic with big draw distance in TR - ash swamps is one of the most cool places in the mod. So in my view it kinda all mostly flat with some minor hills.

Gnomey have other opinion, based on already more complex TR region type map plan that you may see a little bit up in post. This is much more detailed plan that old bethesda one, hovever I think that this moutian bits have absoluetly no logic and it just easy decision how make transition between regions. Also I think that current Moutian regions here borng as hell mostly exept some parts. Only moutian region that should be keeped here is Alt Orethan but it should be detailed and have more uniqle stuff in it to work.
Now, to concrete regions and what I personally want them to be
Nedothril - currently this is bitter coast 2.0. It looks not bad but really not very interesting. For me, best insperation for that place is one of the World of Warcraft zones (zangarmarsh):

This region kinda similar to ash swamp but insted of be dead, it full of life, everything glows and here a lot of glowing mushrooms and water plants
Or this region concept may be used for Sundered Scar region, because lt may have good transition to Dres coast region

Lan Orethan - Gnomey against idea of have forests like this in central morrowind regions, but I think it can be fixed a little bit to make it look more interesting - replace current tree meshes with threes with white leaves. Add more interesting lesser flora to this, make grass and ground textures blu-ish like here

(sorry for bad picture from internet, not finded better refference) and this place be more interesting.

Adittionally, there may be a lot of orchards with blue leaves trees that have some yellow fruits.
So it will be good transition to
Othrensis Plains - region filled with floated plantations where workers and slaves creating materials and manufacturing textile and clothes and aslo natural dyes for them. It have rare pink and white trees, that make it be good transition for Aanthirin region that contain some white elements.

Fauna
This is most important part for look of great House and purpose. At first. it clearly should not contain Stilt Striders, Regular Nethes and skyrenders and most of crab types. They all with their style not fit in this lands and crealy it would be hard for them to survive here. In my opinon most of population here should be Nix Hounds, all kinds of beetles and other similar to them creature, that be major part of Indoril pets, farming, transport and culture.
At first, TR have some generic Green Beetle, Blue Beetle etc. creatures across telvanni lands - they all shold be a little bit edited, got new names snd live avross most of indoril lands. Muskflies can be here too. I think that they should be only in Indoril regions, but Gnomey idea is that Helnim fields can be transition region and beetles may be finded here too.

Nix hound Rikshaw already presented in TR and I find this concept kinda interesting so they may be here, and actual nix hounds match indoril style, also there may be diferent sub-species. My idea is to have nix-hound like creature mixed with firefly for glowing mushrooms region

Other creatures is netch variants for indoril, they may look kinda like this

other concept for transport of indoril is giant beetles insted of stilt striders

Dead beetles may also be used as houses insted of shacks for some dunmers in wild across this regions.
Also Gnomey think that Nix Hound, at least vanilla one not very much fit in Indoril lands, his idea to use other bug-like creature

this is important stuff for indoril since they mostly will use chitin armor, but not regular one - a lit different variants of exotic armor from bugs is what lower class in indoril and lands across it actually use. Most high class use it's own styles of Ebony and Glass armor. Medium tier is use different styles of bonemold armor depends of region

and lower glass styles - where low quality not polished glass mixed with cheap materials such as chitin, bonemold.

So that is. I hope it will help resolf all house indoril concept problems, will show good overall picture of house and it's lands, help resolve problem with roa dyr and actually abybe CAN OF WORMS become not so scary