Hmmm. What happens now?
I log him out to make my update
I change his password so he won't be able to access this account again
I change the email on the account, so he won't receive any notifications
I change his icon to something he wouldn't like, like a picture from Equus
Add to his 'likes' such topics like bestiality, sodomy, buggering animals, abolition of heterosexual marriage, or something else topical
Make a status update of how he's been unemployed and has more time on his hands and has been watching all kinds of porn, and has discovered new things that turn him on. Things he hadn't realized until now
Pick on his FB friends. Maybe target the ones with pets. Ask if he can petsit for them, how he'll do it for free and how their pet looks 'frisky'. Throw in a 'giggety-giggety'
Make an update about how he's got a sweet gig, how he doesn't have to pay rent, but rather, gives oral pleasures to the landlord twice a month, and how he'd do it for free anyway
Add as many creepy pictures as you can into his folders, like many images of horses
Probably wouldn't do anything that bad. Just write in his FB what an asshole he is for messing up your apartment and ignoring his duties
This all takes place before you have a chance to confront him or exact revenge