You can upload an Avatar by creating an account at Gravatar here:

An "avatar" is an image that represents you online—a little picture that appears next to your name when you interact with websites. A Gravatar is a Globally Recognized Avatar. You upload it and create your profile just once, and then when you participate in any Gravatar-enabled site, your Gravatar image will automatically follow you there. This also means that when you want to update your photo, you can update it once in Gravatar and have your photo change reflected on all Gravatar-enabled websites at once instead of having to update it on each of those websites individually.