Sorry, for starters I'd say give up on the team colours idea. I cannot see them working with a brown sectional.

Listen to your mother. Also, if this is truly a "man cave" (ugh), why not let him do the decorating?

Could you have the sofa slipcovered? A deep red twill would be nice, then keep the walls a neutral cream. I wouldn't use anything more than an eggshell finish. The higher the gloss, the more imperfections show in the walls. Don't go overboard with the decor. Some nicely framed pieces and/or a bookcase for memorabilia and your good to go.

@Rina, that's a good idea, thanks! Minus the pillow--there's no way I'd try to incorporate all of the colors in one piece of decor lol And I do love that cabinet...

@torreykm, He wouldn't allow me to do that to his sofa lol

@einportlandor, that's an option, but I have to live here too, and we'll be entertaining quite often in this space, and I'd rather not have an entire part of our house look like a college freshman's dorm room. (His words, not mine!)

Thanks for the help, all!

Some how the term "man cave" suggests the decoration is determined by the man.