Paint the room various shades of grey  You'll feel like killing yourself after a few hours spent in the room.

I wish I'd gone with something a little more 'upbeat' now but the projector dictates much regarding light control. If I'd only got hifi to worry about I'd have a much prettier install:

I particularly like the discrete wall mount absorbers and diffusor panels with maybe some soft lighting behind them. If and when I get round to doing the room again I'll probably try to make it look a little better. It gets depressing after a while in there.