Strange regarding your problems with the avatar. Perhaps it is not a format that the forum avatar generator supports. Otherwise I haven't the faintest idea why.
As for Bezzo's question: I believe that the administrator and higher-tier moderators should be able to change your user name. Maybe not for this forum though, but in many forums that is how it works. And others still have the ability for people to change their own when they please.
Hopefully I shed some light on your problems.
Cheers.