I bumped up a little plugin for my site that generates rewrite URLs for avatar images. So if you visit /avatar/username you get redirected to the avatar for that username. You can add ?s=250 to pass the size to the other side. This is the same query used by Gravatar. Right now, this calls the gravatar URL and does a temporary redirect to it, setting cache control headers to save the redirect. This means that there could be up to two http queries per avatar image. In a future version, I might actually serve the avatar locally. I got tired of broken URLs for my image. Now, the same link will always produce my image.