THere are two wayys to do it, but first, you have to click on “Profile” under the top Pixar Planet banner. The first way to do it is to upload an image from your computer as your avatar. THe second way to do it is to post the URL from a website. Remember, there are a few guidelines for avatars. “Only one image can be used at a time. It can be no greater than 100 pixels in width and 100 pixels in height. There is a file size limit of 40 KB.”
After you are done, click submit. I hope this helps.
I find www.imageshack.us is the easiest to use. No signing up. Just pick the picture from your HD and copy the link it gives you when your done. Wrap the link in tags before posting.