Im having a Birthday Party/Costume party..?

Any Ideas maybe like Celebs like what would be good for that or any ideas on the costume ideas and food and drinks and im not over 21 so no beer or anything like that but i think it would be cool if me and my friend were Paris Hilton and Nichole Richie [because its both of our party's] and were having it at the Renaissance hotel so its pretty nice and having it in the presidential suite.. Help please?