If you would like a picture called an avatar under your user name then you need to go to your profile.
At the top of the forum you will see
Forum Calendar FAQ Search Members Groups Profile PM off
Click on the Profile Icon
Once on your profile page you will see at the top
Information Preferences Signature Avatar Friends & Foes Topic being watched.
Click on Avatar
Now you can select an avatar from our gallery or you can upload an avatar from your computer.
Please remember if you upload your own Avatar that it must be suitable for the forum !