Looks like you found one. Or you could use one of these. Other than that you could use your own and just insert the link in the appropriate area of your profile.
Do you have the avatar? If not, you'll need to locate one. It may need to be re-sized, then upload via your personal settings.
That looks like someone's personal custom avatar... Hmmm. Personal custom avatars were paid for by folks who are Supporters....
Well, I'm guessing that is a Santa Fe steamer. But I cannot think of where it is displayed? Maybe somewhere in California.
How did we do it before? I have a avatar bank in my computer, but no Monads. Did we have a list or resource? Are we left to fend for ourselves? Oh, the humanity!
There was a page on the old site where these were all stored. Now you just open them, grab the url and paste it into the field on your profile. http://www.trainboard.com/highball/index.php?media/albums/avatars.3036/
We also seem to have a slightly larger size here. The old was 150 by 150 pixels. I believe these can be 200 by 200.