I have like 15 avatars I've made. Someone teach me Pro's trick. They're all hawtness. Also sent Maxi an improved one that I expect to see.
You put all the images on a server, name them
1.jpg
2.jpg
3.jpg
4.jpg
...
15.jpg
Then write a script that generates a random number between 1 and 15 and then outputs a url to the image. Point the avatar selector at the script.
Also make it generate a second large random number unto the url, so the image doesn't cache.