Another thing worth mentioning: a carpet (depending on what the floor currently looks like). I have no particular thoughts on throw rugs, but if your floor is ugly and/or doesn't match what you're doing with the room, it'll make a huge difference to cover it with an as-close-to-wall-to-wall carpet as you can.

My last apartment had ugly tiles of the kind I associate with basements, and the rooms basically looked like rooms of some kind that had furniture in them. My current apartment is carpeted, and -- with the same furniture and mostly the same artwork -- it looks like a home.