if you really think you have had a lot of stolen images there is this option
ImageTracker?- The industry standard for image copyright enforcement | Pages - Products & Services
I've caught out a few of mine but never enough to justify this (I have about a 50% success rate with getting paid for the unauthorised usage the other 50% come down really quickly, though only about half of those even reply to the email) the odd one who trys to blow me off I send a letter to the web hosting site (usually the issue is blogs) and they remove it for me