Have them make crazy fan signs for your site.
I'm currently holding two contests at one of my sites:
http://www.fuckingmotherfucker.com/h...ontest2005.php - For the ladies.
http://www.fuckingmotherfucker.com/d...dvdcontest.php - For the fellas (and ladies, if they want).
Those go along the lines of the 'fan signs' idea.