Just as we are landscaping the world, we also want to give the interiors attention.
Morrowind cluttering is actually really showing its age, with lack of detail and general repetitiveness.
They are not individualized to its NPCs, creatures, setting, etc.
More than any other set of tasks we need a small army of people working on these. We're hoping you've already made a house mod in Morrowind, Oblivion or Skyrim and know what its like to clutter a place so that it reflects the NPCs, story, setting and general themes of where you have chosen.
Those that haven't, we'd suggest you go through the Level Designer Series that Bethesda created:
http://www.creationkit.com/Bethesda_Tutorial_Layout_Part_1
You will be savvy enough to be able to look through all of Skywind and Skyrim assets to produce immersive environments. You want to achieve results that make rooms look lived in, or abandoned, or whatever suits in the most realistic way possible.
Just a few small examples; are they rich, poor, have a certain status that would reflect particular layout of objects? All these things can help a place be believable or feel that its being occupied by particular residents. Even if they are nasty creatures, disorganized bandits, proud Nords or master magicians. Use the fact that we know more about Elder Scrolls lore and can leverage from extra assets.
We look forward to how you approach your research and apply that knowledge, both technically and in a lore immersive way.
Also finalizing Navigation meshing for each room will mean that the interiors can be completed for release.
Here are some links about navmeshing, and what the hell navmeshing is exactly.
http://www.creationkit.com/Bethesda_Tutorial_Navmesh
http://www.creationkit.com/Category:Navmesh
Also here a video guide on navmeshing by Bethesda(I think some of the other guides on navmeshing are a little better, but eh)
http://www.youtube.com/watch?v=raM9TBZZyQY

Another useful source of
Another useful source of information for navmeshing
http://forums.bethsoft.com/topic/1464647-the-navmesh-compendium/