Here's my response. I will note for the record that I intend to *make* some of these (not sure which, yet) as soon as I can reliably export from Blender into Skyrim format without vast gyrations. (IOW, I'm not trying to dump work onto others, but rather to contribute to the "to do" list.)
I agree with those who have said "more lights", and would add that both "Fake" and "Off" versions are needed. Invisible Activator objects in various shapes (flat disk, convex "lens" shape, rectangular) with editor markers. I know how to make the Activators but have never had any success using NifSkope to add editor markers. More variety of invisible collision objects, again with editor markers. Booksets that can be used as containers (some have been created, but more variety is always good). Desk/office clutter (static!) Alchemy lab clutter (again, static) Door stones, like the ones in Oblivion Some flat stone platforms in various textures and shapes, for use with outdoor craft areas, shrines, etc. Retainer walls with and without embedded staircases, as a tileset, with attached flat "land" on the uphill side (these exist in vanilla as "terrace" pieces, but limited in variety) Standalone water statics like the ones Washington (?) did for Oblivion. Maybe these exist in vanilla, but I haven't found them yet. Wall decorations that are not pelts or flattened basket weaves (booooooorrrrrrring!)