If you've got nothing else, look in the mirror before you go. Pick something. Scar on the cheek, brown eyes, good physique, etc. Pick one thing and talk about it. I got this scar when I was five.... No one else in my family has brown eyes, my sisters always said I was adopted but when you're from a big family...
You get the idea. Everybody has something. Not everything fits into 4500 characters on a website.