If it's large enough, put a pool table or ping pong table in the center (I'd go with a pool table). Set up a big screen in a corner, with games and stereo. Put a couch near the tv. You can have a ddr mat or two near the tv, etc. Combine this with all the other game room suggestions (sports memorbilia, bar, disoc, etc.) and you're good to go.
No I was thinking of a "tramp", woman of ill repute, that you jump on in the room. You know, get busy.
13x13 is a pretty small room. If you have money, buy a large flat screen TV that you can mount on your wall and it might be serviceable as a media room. Sounds like you've really thought of everything already.
