one word to brighten up any apartment - toile - use toile for wall hangings, room dividers, even (with a plastic liner) shower curtains - JoAnn's always seems to have some marked-down toile
Depends on what kind of texture you want - venetian plaster is easily enough made - has anyone ever tried the faux leather finish on walls and furniture that Frank used on Trading Spaces, with torn up garbage bags and a lacquer?
the key to your question is "reasonable to accomplish" - some of the trading spaces and while you were out stuff cannot be (and should not be) replicated - Debbie Travis has some good stuff
I used to live in a newer (1989) townhouse - could hear neighbor's treadmill, not much else, but that may just have been because he was quiet - in older townhomes and half-doubles, you can hear everything.