When I changed my email address on my profile, My avatar picture changed. I do not like the new one. Why did it change, and can I get my old one back?
The avatar is generated from an MD5 hash of your email and is served by gravatar. If you change your email id, then logically, the avatar changes. The simplest way to have consistent gravatars that you can control is to register for an account at http://en.gravatar.com/ and set your image.
I've used your old email info from your user history and its MD5 hash, to obtain the URL that gravatar used for your previous avatar. Here is the image in 512x512 that you can now use and set as the default for your current email in gravatar.