If you want a custom picture, though, you have to go to the User CP (which has a different location depending on which page of the forums you're on) and then click "Edit Your Avatar" under the "Your Profile" section - NOT the one next to the ad.
Of course, you can't change your title from that particular avatar editing page, which is what you want, but I figure as long as you're messing with avatars and titles you'd want to know where the other options are. Why aren't they all in one place? I don't know.
Edit: The link in the second post worked fine for me. *shrug*