Just stay away from anything that has been rabid in the convention community. If you can score the internet for previous masquerades, take note of the songs that have been repeated over and over and over. I'll bet that Gangnam Style is going to dominate skits this year. If you can find a way to connect your cosplays with a particular tune, all the better. It'll connect with the audience better too. Judges will appreciate the extra thought and award more points.
Fear the storm, it's coming.