Clean: No
Plenty of dirt cells
Region "delete me" is not deleted
Take a look at this https://www.tamriel-rebuilt.org/content/utility-tesame
Consider naming all the cells important to your showcase and deleting everything not named, though I wouldn't recommend keeping this habit for claims

Everywhere
Some under water flora clusters are too packed while the surrounding area is undetailed
Hlaalu doors should be set further in the frame
ex_hlaalu_dsteps_03 shouldn't be used under balcony steps, but need to be used on every other ground level opening
Lanterns should be resting on their hooks without bleeding or floating.
Some buildings have butresses way too close to the corners
furn_de_signpost_02s need a banner
Tops of the guard towers need trap doors
Check wireframe (W) to look for rough and spikey terrain
Even though the West Gash doesn't have vertex shading between textures, you should get in the habit of doing so here since that is TR standard

Gash Island -16,6
In the top left corner there is a Flora_kelp_03 that is sunk too deep in the ground, and 2 in_cave_plants that are resting on one point that should be sunk more
In the rock cluster at the bottom, I would avoid using such large rocks like this, since most of the rock is hidden under ground you can use something smaller
In the big rock cluster near the middle there is a lighting seam, the blue coast ref should be raised enough to hide the seam
There is some rough terrain that should be smoothed between the bottom right side of the terrain_rock_wg_10 in this group, and the rock arch in the next cluster
Every cluster of rocks under water has an arch, rock arches should not be this common
On the shore there is a Terrain_rocks_WG_03 hidden under terrain that should be deleted
Below the hlaalu building there is a Com_Chest_11_moonsugar that is hidden under terrain and should be deleted
In the bottom right at the top of the hill and under the trees there is some rough terrain that needs to be smoothed out
On the hlaalu balcony, the furn_de_rug_big_06 should be bled into the floor a bit so the tassles are barely floating. This will always be the case with rugs like this
There is some rough terrain that needs to be smoothed below the balcony on the north
Pathgrid on the balcony is unnecessary 

Gash Island -15,6
North road by the coast is rough and spikey
Terrain_rocks_WG_03 on the east border beneath the road is floating
Terrain_rocks_WG_04 beneath the road and between the 2 stair cases is caspering, which means that one or more back sides with no model face are showing
This area has more rock groups than needed
flora_stoneflower_01 on the coast in the west has a leaf bleeding into a rock
flora_tree_wg_04 on top of the hill has a branch bleeding into a hlaalu building
terrain_rock_wg_08 on the west border by the coast is missing vertex shading
flora_tree_wg_06 near the west border has branches bleeding into a hlaalu building
I don't understand why the ex_hlaalu_b_02 in the bottom left has entrances facing the wall instead of what appears to be the town square
Some of the barrels on this building are floating because the floor is slightly sloped
Lots of bleeders on the 2 furn_de_ex_table_03s on the roof of the ex_hlaalu_b_18. Consider using the much easier de_p set instead of these nightmare tables
The walls connecting this building and the neighboring ex_hlaalu_b_03 look bad and block what could have been another path
Too much vertex shading under these buildings
flora_tree_wg_06 by the curved wall has a branch bleeding into a hlaalu building
flora_tree_wg_05 by the curved wall and the north west gate has a branch bleeding into the wall
Some sacks on the top of the guard tower need to be sunk
ex_hlaalu_buttress_04 on top of the steps to the ex_hlaalu_b_24 are not meant to be used like this
Crates south of the ex_hlaalu_b_24 and on the west side of the wall are sunk too deep
barrel_01_saltrice beneath the guar tarp and between the 2 butresses of the ex_hlaalu_b_05 isn't resting on enough points
furn_de_overhang_01 on the south side of the ex_hlaalu_b_24 should be raised a bit so everyone can fit under, and all the furniture under this tarp are bleeding into the ground awkwardly
Crates by the south west corner of the ex_hlaalu_b_06 are all sunk too deep
misc_de_bowl_redware_02 on the balcony with the 2 small tables between the gates is sitting on one point, weird pointy bowls like this can be bled into the surface
potion_comberry_brandy_01 floating above a chair that is bleeding into a ex_hlaalu_b_11 left of the north east gate
Table on the stair case balcony of the bent building make the doorstep look too cramped
Some baskets under the guar tarp of this house are sunk too deep into the ground
Drinks on the de_p table on the balcony of the building in the bottom middle are bleeding into the table
furn_de_r_chair_03 floating above the balcony of ex_hlaalu_b_09
same balcony has a floating basket with eggs bleeding through the bottom

Gash Island -14,6
Texture seam showing on the shore north of the big arch
The road terrain is extremely rough and spikey, especially where the road touches the canal
Floating crate on the north side of the canal
Crate bleeding into trim on the south side of the canal
All sacks on the canal need to be sunk a bit
Terrain_rocks_WG_02 on top of the hill in the bottom left, this type of rock group shouldn't be used like this
flora_tree_wg_03 by the south border in the middle has a branch bleeding into a rock

Gash Island -13,6
Texture seam showing on the hill by the shore, next to a terrain_rock_wg_01
Spikey terrain that needs smoothing on top of the hill by the terrain_rock_wg_10

Gash Island -12,6
Spikey terrain that needs smoothing south of the tomb entrance
Land is under detailed

Gash Island -16,5
Another huge rock arch here not being used as an arch
Terrain_rocks_WG_02 north of the temple caspering and upside down, don't use these like this
Most trees by the temple have leaves bleeding into the terrain or a rock
Top of the hill in the north east corner needs smoothing
Terrain_rocks_WG_04 at the bottom on the shore has a caspering rock, and should be moved further into terrain so less rock is showing

Gash Island -15,5
Some rock groups on the beach are missing shading
Road is EXTREMELY rough and spikey
Trees by the south gate have leaves bleeding into the buildings
flora_tree_wg_05 by the rocks on the east border has leaves bleeding into the ground and rocks
flora_tree_wg_03 in the town has branches bleeding through buildings
ex_hlaalu_wall_01 hidden completely in the bent building and should be deleted
ex_hlaalu_b_22 looks weird to be partially blocking the gate like that
furn_de_forge_01 seems randomly placed
ex_hlaalu_b_05 rotated building? Why?
furn_de_r_table_03 north side of the guard towers bleeding into wall and terrain
The wall attached to the north guard tower seems pointless
Door to south guard tower out of frame

Gash Island -14,5
Road is well smoothed in this cells
flora_chokeweed_02 between the grove and the road has the bottom of the stem poking through the top of the terrain
Terrain spike by the east border between terrain_rock_wg_09 and Terrain_rocks_WG_01
Terrain spike south of the ex_dwrv_ruin10 just on the edge of the road
Terrain spike near the east border to the right of the terrain_rock_wg_08 where the scrub meets the corner of that brown texture
Brown hill on the south border by the beach needs smoothing

Gash Island -13,5
Rough spikey spots along the road
A stoneflower in the bottom left corner, above the road and by the dwemer tower has a leaf bleeding into the ground
Terrain up the hill north of the dwemer tower is rough and needs smoothing, and there is a big spike on the scrub
Terrain_rocks_WG_01 near the top right on the brown trail is hidden under terrain
Most of the hill needs smoothing
Terrain_rocks_WG_01 by the north border is caspering
Terrain_rocks_WG_03 in the middle, close to the top, is floating

Gash Island -12,5
Texture seam near the bottom left where rocky scrub meets scrub and brown texture
Land is under detailed

Gash Island -14,4
Rough spikey terrain by the north border and the shore, to the right of some trees. Continues to the half way point of the border and cave entrance
Entire hill has rough terrain that needs to be smoothed

Gash Island -13,4
The road in the dwemer ruin is very rough and needs smoothing
Terrain_rocks_WG_04 in the top left thats sticking out of terrain_rock_wg_10 like that does not look good
Terrain_rocks_WG_02 in the bottom left is hardly showing, should be moved to be more visible or deleted
terrain_rock_wg_01 at the bottom of the circle road is caspering 

Gash Island -12,4
Texture seam slightly below a rock group at the beginning of the road in the top left
One of the plain brown trees is missing vertex shading
Terrain_rocks_WG_04 south of the rock cluster and by the salt rice, shouldn't be used like this
2 large rocks underneath the terrain below your huge rock cluster
On the right side of the rock cluster there is a large rock being used as a small rock
Consider replacing the terrain_rock_wg_10 in the cluster with terrain

Gash Island -13,3
Rock group covering texture seam on the beach needs vertex shading

Gash Island -12,3
Rock group covering texture seam on the beach in the east needs vertex shading
Texture seam below the wooden dock
Rocks by the dock need vertex shading
Dock is very high up compared to the boat
Road is well smoothed except for a spot in the west under a terrain_rock_wg_09

Comment time
Your path grids are all well done, your paths are very well sunk, you seem to have covered most of the texture seams, and your vertex shading is mostly good. You also shaded around the coast which is really good. I don't really understand the layout of the town or why everything is so rotated, but you do have a pretty good level of detail here. This may seem like a huge list of errors but your showcase was just pretty huge in general so don't worry about it. Once you fix most of these errors you can be promoted for exterior development.

Reviewed interior

Name: TR_Othmura_8_Travelling Merchant, no longer for a claim so should just be TR_showcase
Clean: Yes
Lighting: Sunlight setting too high should only be 10 on its various settings, ambient lacks colour. Could use additonal light sources.
Northmarker: Present, good
Fits exterior: NA, but fits a ex_hlaalu_b_05
Pathgrid: Several paths clipping and one area lacks a node, see images on discord
Illegal to Sleep Here: Yes, correct
Gridsnap: Good
Tileset: The entire shell makes ineffient use of pieces, hlaalu "hall" peices and room entrances would solve the issue of adding posts and the seperate wall on the top floor.

Bleeders:

Floaters:
misc_de_bowl_white_01: should be bled to hide the point
bk_PilgrimsPath: this would fall off the sacks, find a better spot
chest_small_02_silverwa: floating off the edge of the book shelf making bottom of chest visible

Other: 
the three sacks next to the bed just looks odd.
The bed itself could be scaled down to 0.9 to allow movement beside it
Needs tapestries on some of the walls
This needs more clutter, just in general, more misc items, some potions, ect.

Reviewed
Name: TR_Interior_Showcase 
Clean: Yes
Lighting: Okay
Northmarker: Present, good
Fits exterior: NA, but fits a ex_hlaalu_b_05
Pathgrid: Good
Illegal to Sleep Here: Yes, correct
Gridsnap: Good

Bleeders:

Floaters:
misc_uni_pillow_01: not resting properly on bed.

Other: 

Tomb has agreed to do another pass on the clutter, other extant issues have been fixed aside from the pillow

Name: TR_Interior_Showcase 
Clean: Yes
Lighting: Okay
Northmarker: Present, good
Fits exterior: NA, but fits a ex_hlaalu_b_05
Pathgrid: Good
Illegal to Sleep Here: Yes, correct
Gridsnap: Good

Bleeders:

Floaters:

Other: 
tapestry placement needs to be corrected, see discord for example. They should also be at the defat scale and the two next to eachother should be replaced wiht one placed properly.
the silverware cutlery should be wood cuttlery as this is a poor int
the marshmerrow is in a misc vase, use the static version or a proper plant pot

Fix these last few and I will reccomend for promotion.