Don't know if it is allowed, but messing with my profile last night I was able to upload a (very small) avatar. I have pm'ed a moderator to see whats up.
If you are allowed, this is how you do it:
First get a pic from your photobucket account.
Shrink it to 30x30 pixels or less.
Copy the direct link.
Go to the trx forums and click forum actions, then edit profile.
Click edit avatar.
Click use custom avatar.
Erase the http//www. in the box and then paste the direct link in.
Click save changes, and you should have your own little avatar for all to see 8°))