I think I've seen a user put a picture into his post inline. How is that done? I'd like to be able to embed images of problems/questions, rather than describe them.

Please check the following help page: http://www.llblgen.com/TinyForum/Help.aspx

Also, one option is to attach the image to the message, check the "Add Attachment" checkbox, below the Message body editor.

You can refer to a picture if it's somewhere else, like:

which uses the [ img ] http /... jpg|gif|png[ /img ] tags

ooo, my head spins at the possibilities.