That's basically what Gravatar has recently adopted (http://blog.gravatar.com/2008/04/22/identicons-monsterids-and-wavatars-oh-my/ http://blog.gravatar.com/2008

That's basically what Gravatar has recently adopted (http://blog.gravatar.com/2008/04/22/identicons-monsterids-and-wavatars-oh-my/ http://blog.gravatar.com/2008/04/22/identicons-monsterids-an...) for non-users, and it is equal parts tacky and useful. I'm not sold on the idea of something like this here, but even a very small icon (like 16x16 or smaller--very small) or bullet of color would would make threads easier to keep track of.