Try something like, “Blondes may have more fun, but being a brunette, if we have fun, I'll still remember it the next day,” or “I'm a manly man, but I will eat quiche on occasion and may even share the remote control once we get to know each other.” Most people want to appear as attractive as possible in their dating site photographs.
Use your profile picture to show that you are cute and funny, too.
Post a photo of yourself up on stage at the local comedy club, or perhaps, posed to resemble a Weird Al Yankovic album cover.
Wear a pair of oversized sunglasses or “draw” a moustache on your picture with a photo-editing program.
Again, change your photo frequently to keep things fresh.