Depending on how many people you have attending your party, you could set up a group of anonymous judges. Just ask certain people (5 maybe?) who they think have the Best, Scariest, etc. costumes of a list you have compiled. You yourself could choose the Top 3 or 4, and have then tally up what your anonymous judges say. That way, you don't take up a lot of time, and even the judges have a shot at winning!