Lord Gruffles, that's your URL avatar. To change or confirm, do the following:

1.) Go to User CP
2.) Click on "Edit Profile"
3.) Scroll down to the very bottom of that screen
4.) The second-to-last row should say "URL Avatar". To change it, simply click on the "Gallery" link, and from there you can select from a number of avatars listed -- including the one you currently have.