What's a good party theme for a formal dinner?

I’m in charge of hosting a 80+ person party for my dorm sisters and their dates. This is our sophomore initiation formal, which usually includes some sort of catered dinner and games, music, etc. We usually have a theme, last years I helped coordinate a Masquerade theme, the year before that we all dressed up like movie stars,and the year before that we had a secret agent theme.

Because my dorm has the tradition of keeping this a very “dressy” occasion, it makes it a little harder to pick a theme. Do you guys have any suggestions?