Hmm. Interesting idea. I have never seen a image to BBCode converter before but I have seen image to CSS code converter. I think the main reason is most other forums allow images and there is no need for image to BBCode converter hack - well, Bitcointalk excluded of course.

With the [glow] [/glow] BBCode, I think we will be able to achieve that - however maybe only for small 'pixelated' image.

                                                                       

However I am not too sure as I am new to BBCode styling too. Just styled my new signature from scratch and saw this post (check my signature out :p).