I changed my avatar to a test image from no avatar at all, but some pages (2 days after the change) are showing an older avatar I used. What gives? 
Yes, that. My profile looks fine, but some pages (like this one) are showing an older avatar, that looks like a blue jellyfish with yellow tentacles.I see the test image no problem. You mean the different colors like bar tones?
Clear your cache and/or refresh the page.Yes, that. My profile looks fine, but some pages (like this one) are showing an older avatar, that looks like a blue jellyfish with yellow tentacles.
Nuked the cache, reset Safari, yet it still won't use the new one... I wonder if that's because I'm connected via a proxy server at the moment.Clear your cache and/or refresh the page.
Avatars always have a nasty habit of sticky around in cache.
Yeah, I think it's the proxy... just tried from IE instead of Safari. Same issue.your 'test' image shows up just fine here, and seems like its working for others. try a different browser? perhaps it is the proxy?