I've developed a Google App Engine project that creates static links for user profile images.
This is the format for the static link:
http://spiurl.appspot.com?screen_name={screen_name}
You can use my service or download the code here -
http://code.google.com/p/spiurl/
It is a slower process, but it might be acceptable for many
applications.
I'm currently using it on My Tweeple (http://mytweeple.com)
Of course I make no guarantees of performance or stability. ;)
