You could go for a certain time like the 50's or the 20's (Great Gatsby), you could have movie or red carpet theme or go for a "ball" theme. Depends how much money you've got to spend I guess and if all your friends would be willing to dress up.
Fancy dress in general is always good fun... If you wanted to go for something more specific then maybe like a prince and princesses theme or maybe Masquerade theme, where everyone wears masks and ball gowns, for something a bit more glamorous.
Theme everything around ALIEN! have hundreds of hand made cocoons filled with voilent creatures such as pythons or Boa's (possible camel spider/scorpions) Then when guests arrive, send them into the room, and blind fold them, and tell them to search the egg sacks.
Well make into a hollywood theme
Hawaiin theme,punk theme,roses and butterflies,stars theme,valentine's theme (hearts),under the sea theme with sea shells and stuff,make sure you make your invitation cards according to the theme.
Definitely the 1920's with the dress code for that era - check online. You will be able to research it all on the net.
you could have a party theme of hollywood .
old hollywood, the great gatsby, a night in paris or red carpet
Vicars and tarts.
I want a theme that is glamourous and quirky for my 16th birthday party. If you think of a good theme, please suggest some ideas for the party that go along with that theme too! Thanks