While browsing this site, you may have noticed in the comments that some people have photos and some don’t. Well, WordPress uses a nifty service called Gravatar that allows you to create an account and setup photos to be used in comments on various sites.
It allows you to enter multiple email addresses and set a different photo for each email (as seen below). All of this happens automatically with WordPress once you’ve created your gravatar account. You might have to wait a few minutes for it to become active.