First off, awesome plugin!
I have a small request though. Could you please add a custom option to add additional parameters to the linked image?
Ex: I use 'lightbox' on my blog to load live/bigger previews of the image when the user clicks on the thumbnail. You can see it live at: http://www.igvita.com/blog/ (Bottom of the page, any flickr image).
Now, lightbox knows to preload the image when it sees: rel="lightboxflickr" as part of the <a href... > string.
Hence the request, I'd like to automatically add the rel="lightboxflickr" line to all linked flickr images. I can do it manually at the moment, but automatic would be plain awesome!