There are two different pictures.... A profile picture, and an avatar.
You *do* have a profile picture, which I can see here: http://www.bettafish.com/member.php?u=46097
-- but that's only visible when people visit your Public Profile page.
You also can add an avatar, which shows up on the threads (like this one). To add an avatar:
1) From the top left of the screen, click User CP
2) On the left menu, under Settings & Options, click Edit Avatar
3) Under Custom Avatar, click Use Custom Avatar, then upload an image or enter a URL