I think having a room with exercise equipment, like treadmills and exercise bikes, would be good. Exercise is such a wonderful tool to use, and yet so few people use it. In the hospital I go to, there is only one exercise bike, and in one TV room there is a Wii which provides some movement. There are walking groups and groups where you can go to a gymnasium nearby to play games like basketball/floor hockey. I think these are all good things to have.
I also think groups are important to have as well, like meditation groups, art groups, etc.
Boredom is a huge problem in psych hospitals, which does not pair well with depression and other mental illnesses!