Despite Google Image search existing, perhaps there's still an opening for a site where you register your work; thus creating an easy place for people to check when looking for owners (i.e. if an image is used all over the web Google may return thousands of results leaving the originator hidden several pages into the results; assuming the places which have used this content haven't provided an easy means to get back to the original / haven't included copyright info this may be hard to track). Image search engines could also use metadata from this site to provide a side bar summary about the image's ownership and licensing info.