Okay, LESSON TIME, children. Put down your pencils and put your listening caps and thinking ears on.
To turn off avatars, go to "User CP" in white letters in the blue bar at the upper left side of each screen. You can see this no matter where you are in the forum.
Then you will see a list of blue words against a gray background on the left. Under "Settings and Options", click on "Edit Options".
A series of boxes opens up in the main part of the screen. About halfway down, one of them says, "Thread Display Options". Right below that, it says "Visible Post Elements". Here, you can check or uncheck the boxes depending on which images you want to see. You can block all images, or just avatars, or just signatures, or any combination. If you leave the Box UNCHECKED, you will not see those elements. Unfortunately, if you block signatures, you block the written part too.
When you are done, go to the bottom and click "Save Changes.
You can adjust lost of other things in the Control Panel. This isn't rocket science. You won't break the internet if you fool around in the User CP.