reviewed
Name: SHOWCASE, when your making claims they need to be marked "TR" so this should be tr_showcase
Clean: no, Hound meat
Lighting: Pretty good start, few things. "sunlight" generates light directionally ingame which can look odd depending on the circumstances, so as a rule keep it low at around 10 (all the way at 0 causes issues of its own). Your ambient settings okay, but should  sit more in the brown-orange range, this matches better with candle light making ints feel more maintained and "homey"
More direct you have a single instance of green light from the light_de_candle_02 on the small table downstairs, if you replace that with the 64 variant like upstairs this should be fixed
Northmarker: present good
Fits exterior: Yes, fits shell claimant specified. Minor note, you can actually extend these out a little to the stair section (or the landing at the top of the stairs to be exact)
Pathgrid: Absemt, https://www.tamriel-rebuilt.org/content/tutorial-pathgridding-tutorial < this tutorial will explain how to make one.
Illegal to Sleep Here: yes, correct
Gridsnap: good

Bleeders:
Misc_Quill: bleeding into the inkwell side

Floaters:
Misc_Inkwell: floating a tiny amount
com_sack_02: should be bled into the floor a little to mimmick cloth physics

Other: 
Your tapestries are placed a little low, should be higher and sticking out of the wood rather than the wall.
Could use a little more clutter, prefferably from the tamriel data items. (obvious exception is the fixed de_p furniture, otherwise free game)

Fix the above issues and I will reccomend for promotion.