hollywood theme - ask everyone to come dressed in black and white.
80's themes are always a lot of fun, everyone dresses 80's style, you could set up a few tv's each showing a different show from the 80's., play 80's music, etc.
You could do a party as if she were turning 6. Like have a pinata, decorate with really bright colors, play pin the tail on the donkey, etc. I did this for a friends 26th birthday and it turned out really well. I have pictures if you want ideas.