And, could this tool support other projects?
I wrote http://toolserver.org/~multichill/nowcommons.php a while ago, less colorful, but should work on every wikipedia.
Many other projects have copied PD images from en.wp, and those images have since been moved to Commons. It would be a great help to be able to quickly go around the smaller projects and assist them to use the images now on Commons, and remove the duplicates. I was just now doing this over on en.wv, and was thinking that I need a tool to help find the dups!
At the nl wikipedia i created a template a while back to mark images moved from other wikipedia's, but not yet transfered to Commons. The template makes the images end up in http://nl.wikipedia.org/wiki/Categorie:Wikipedia:Afbeelding_afkomstig_van_ee... This can be very useful to mark images and later transfer the source images to Commons.
Maarten