But since this is a gay site, let's think about the other important aspect... how to decorate it? Mine has had plain white walls for 9 years now, and looks incredibly stark when photographed. What are the best gym colors? Other design choices?
I was thinking of going with some bright energetic colors and maybe some posters. But somebody suggested adding some restraints - and maybe a sling - to the squat rack and going with a dungeon motif.
Well, certainly, adding a 'playroom' aspect could be hot... but then you'd also have to have some versatile 'mood' lighting installed. Maybe a big plant if you have the natural lighting for it? Maybe mirror a whole wall as well? Tan walls?
I'd go with some vintage, black matted and framed 1950's cover drawings from gay men's pulp porno books (look on Ebay). I have three separate pencil drawings by ADAM - cop/boy; boys wrestling; coach with boy in rope restraints which would look great on your walls!
But we'd have to partners, first, for you to get them!