TinEye Reverse Image Search is a pretty cool search engine that lets you upload an image, then find it somewhere on the internet. It crawls the interwebs to find out how the image is being used, where it came from, and can even find modified versions of it. You can also get a plug-in for it so you can search for images just by right-clicking them. Plug-ins for both Mozilla Firefox, Internet Explorer, and Chrome are available.
Some argue that you can use it to find edited versions of your original artwork—possibly palette swaps—by uploading your image. It's not that great, so you probably won't find any of that CP you wanted, you sicko.
TinEye is a piece of shit so far, but you can help by submitting websites for it to crawl. Hopefully, the people who review the submitted websites aren't conservative Christians who want to censor everything that threatens the safety of their children. You can, however, upload gory images of crime scenes and get results, so censorship doesn't seem too likely.