AFAIK it's hundred posts before you can have an avatar or post images.
Only paying members can attach stuff (I think) and as payment is not possible at the moment…
You'll need to have your image hosted someplace else -like ImageShack or Photobucket
- and use IMG-tags to post it in-line, like these:
(well, xcept for the little yellow feller of course)
But you can post a link to your image