I have to "takeover" my sorority mom's room on halloween...ideas?

My "sorority mom" is a sopre, I am a freshman, and on Halloween we have what's called "takeover". This means we have two hours to go in our "mom's" rooms and take it over, in any way we want, so we can mess it up, decorate it, whatever we feel like doing.....I don't have many ideas, but I do know I only wanna spend about 40 bucks!! Any ideas?