My husbands "man cave" fantasies...

With my oldest daughter moving, my husband has decided that the basement where her bedroom was will now become his "man cave" where he can put all of his fitness equipment and be able to work out. Right now he uses the garage since it's warmer, prior to that he used the living room. I keep telling him considering we have two other daughters that have moved in and moved out that I wouldn't overly decorate if I were him, yet the dream of the man cave seems to be one he doesn't want to let go of.