I want people to upload avatars on my board from their own computers, but I would also like to moderate (review before I accept) those avatars. I don't people to upload porn and stuff as avatars. I suspect that this is yet another important function that this board lacks, but you never know, so I have to ask. :)
I don't think that's such an important feature, to date no one has done this on my site, but if they should its much easier to deal with once seen or reported by another user than to have to check every avatar, not to mention having to re-approve avatars again when users decide to change them.
Feel free to make a request in the mod request board (http://www.simplemachines.org/community/index.php?board=79.0) and see if someone's willing to do this for you.