It took a bit of work to get custom avatars up and running. I've allocated space on the server for people to upload their own avatars, and that's now been tested and seems to be working.
FYI, for future server performance, you'll note that many forum sites disable the uploading of custom avatars because it increases the load on the server when viewing threads with lots of posts with local avatars. External avatars of course don't cause that load.
