Decorations like: dead branches, flashy thingys, horny portraits (sounds vulgar) and stuff like that? and if you decorate well and the feng shui of the room its perfect, something nice happens.
No seriously...
Edit: Hell now that i think about you can even give your creatures a mistress poster for they're lairs








. Of course the decorations would have to be evil they couldn't be rugs and wall hangings. The motto is 'evil is good' not 'knitware is good'






