The first thing that comes to mind is Maudi Gras ( I know the spelling is wrong, but I hope you get the idea). I think this would be a great theme, no matter what time of the year it was held.

We are going on our 4th year of a parent's night out, including a silent auction and dancing to a DJ. It's been a big success, and all money earned in the past has gone to our playground we installed last summer. This year we have a new cause, and wanted to shake things up with a theme. We all decided that we don't want costumes, but just something to keep it interesting and exciting.
Has anyone done something similar? I'd love to hear your ideas.