Here is the advice from John Duncan on how to post pictures:
2) Picture uploads should work, too!
- To upload a picture, you'll first need to have it stored on a site such as Flickr or Picasa.
Copy the URL of the picture, then click the little 'tree' symbol on the menu bar of the Forum posting window, paste in the URL, and click the 'insert' button.
Pictures should be no wider than 400px – there’s an option to set this in that box.
More picture-posting advice in
this thread.