It depends. Some costumes are actually trademarked (i.e., Lady Gaga has a registered trademark in the costume international class). You should hire legal counsel to do the research and review the footage.

I agree with the above counselor at law; it really depends. Intellectual property is a somewhat "constipated" area in the law meaning that it hasn't really changed much over the last few years. When the laws were settled, long ago, nobody even imagined digital cameras, instant digital photography, the ability to upload to websites for the world to see and even to make money. That being said, since you said you are submitting a "commercial" ad for a national advertising campaign contest, you most certainly need the guidance of an intellectual property lawyer to keep you out of "hot water". If it was just pictures for friends and families on Facebook, that is one thing, but because you are profiting, that makes things a little more difficult. ESPECIALLY if the costumes relate to modern personal likenesses like Katy Perry, Lady Gaga, Britney Spears, Paris Hilton, etc. etc. etc. I doubt the costumes you are referring to relate to anything over than 80 years old like Charlie Chaplin, et. Al. Those would be public domain but then you still have to consider who MADE the costumes because everybody wants to get their "cut of the money" if you are profiting. Hope to here from you, this is my specialty by the way. Good luck either way, but hire an attorney...any attorney, that knows about intellectual property.

If you make the costumes yourself, I don't think you'd have a problem, even if they are caricatures of celebrities. Not so with costumes created by others; those would carry rights with them and you could not freely use them without a license.