Take a picture of yourself right now. Don’t change your clothes. Don’t fix your hair. Just take a picture. Post that picture with no editing. (Except maybe to get the image size down to something reasonable. Don’t go posting an eight megapixel image.) Include these instructions.
owlfish prompted me to try using PhotoBooth - that application has always terrified me (who wants to sit at the computer looking at a full sized picture of yourself, warts and all!). I also remind you that here it is the middle of the night, so you are looking at an insomniac, in tatty t-shirt night wear :)