I learned how the avatars are stored while I made the avatar forum hack, I'll think this one over and give it a go tonight or tomorrow. I may add a new table to act as a temperary holding spot for the avatar link, before it is approved. I guess if they upload an image, or put in a link, either URL can be stored into the temp spot until admin approval moves it into the user table. This would store the URL, but not have it used until admin approves. You guys think that a PM to the admin is a good idea? Maybe I'll just add a config setting for the PM. Busy site admins would just goto the avatar approval page once a day or whatnot.
I'm gonna make this a seperate hack, so you can have the page of forum avatars be used right away, since they are already pre-approved.