My 'studio' is also my general computer room, file storage, instrument storage, and dog-laying-around room. It's about11'2" x 10'4", carpeted, oak-wall paneled, drop-ceiling, and has a dining room buffet, and steam radiator (covered) with cabinet above, 2 windows, 3 door openings (only 1 with a door), plus my computer desk, a file cabinet, bookshelves on 2 walls at head height and above, a 5-ft tall open cabinet I built to house all my guitars in 1 place (with another double shelf on top of it filled with DVDs!), plus the rest of my equipment - small amps, mixer, mic stands, cables, etc.
Now the band has broken up, that means my 2-tier keyboard stand, 2 keyboards, another amp (2x12), amp stand, another mic stand, 5-guitar stand all need to get fit in somehow.
Acoustic treatment? HAH!! I'll be lucky to be able to fit my desk chair in there!