hmmm... ideas...
i can think of loads of stuff. most of them fairly weird
movie characters (i.e. indiana jones, top gun etc)
cartoon characters (smurfs, flintstones etc)
pop stars (metal bands like gnr are always fun to dress as. or go as snoop dog
)
a theme where you dress as anything beginning with a letter. so say p ... you could go as a pimp, protester, phsyco, priest, pervert, peanut... the list goes on
beach theme? chicks get to go in bikinis ...totally sweet
sports theme? marathon runners? jamiacan bobsleigh team?
sick look theme? basically wear the most disgusting and random stuff you can find in the markets. ie sauce pan on your head and freaky dyed flairs or something
there are more. give me time