How to make the party fun??? Do you remember how does usual party look like? People gather together, drink a bit (or more) then dance and communicate. That is all… Boring.
To my mind all parties should differ from each other and should bring something new in our life not only headache;).
I've got one idea for the party and want to share it with you.

For that evening buy water-colour, and invite your guests. But you should remember that you would better clear the room from some expensive things (if you don't want to spoil them). All your guests should have with them are swimsuits.
Then offer them to put the swimsuits on, give them water-colour and ask to cover each other with drawings. Some alcohol and music are plus. Then you can announce a contest for the best body art or just continue having fun.

Hope this will help you to diversify your parties.