It's called an Avatar. Avatars are small graphical images that you may choose in your profile. They are displayed below your username on all posts that you make. You can select the image that best describes yourself from your profile options.
First you need to go to
and then go to
Edit Options. The very last option on the page will be:
Change Avatar. Then just upload the picture you want to use.
Sure sounds simple dosen't it?
