This site is now Gravatar 2 enabled. If you have a Gravatar set up, then you will see it next to your comments. If you want one, go to http://site.gravatar.com/ and create an account.
If you don’t have a Gravatar, then you will see the following default image by your comments:
If you are interested in getting this set up on your own WordPress blog, check out this site http://zenpax.com/.