Edit: Hang on. Worked in preview, then seemed to change.

Edit2: Now I'm curious. This (long url format):
[ url =www.google.com][img]http://i.imgur.com/me5uZ.png[/img][/ url ] (remove the spaces before and after url)
works when the post is previewed, but then turns into this
[img]http://i.imgur.com/me5uZ.png[/img]
When the post is actually made.
Are picture links removed because of the image scaling? I know I've seen at least one linked image in a signature, though.
Edit 3: Nevermind. Putting a single character before and after the image tags makes the link work. Which... seems odd to me, but I can live with that. That fact that it's possible to get a different actual post than what appears in the preview with the same message text is very strange.
[url=http://www.google.com] [img]http://i.imgur.com/me5uZ.png[/img] [/url]
gives: