Well, I got tired of waiting for the avatars to come back. So I did something about it, and now I can see almost all the avatars in this thread!
To do the same:
1. Get
The Reiconizer and install it in Firefox with Greasemonkey, or in Chrome.
2. Download
this file, which contains all the avatars I had in my cache. Extract it and open it in a text editor. (Beware: it's 3.5MB uncompressed!)
3. Locate the source for The Reiconizer, and edit it. In Greasemonkey you can just right-click to edit it. In Chrome you have to find the weirdly-named folder where it was installed.
4. Copy the 3.5MB of text and paste it after the "Give a particular user a particular icon. Top priority." section.
5. Save, and possibly close and reopen your browser.
Good luck! P.S. Side effects may include AT users' icons appearing on other people on other forums, and avatars from Wikipedia displaying for some users. To get rid of the Wikipedia avatars, click Quick Links, Set default avatar(s)..., type "none" in there, and click OK.