I've been doing a lot of copyright infringement work so i figured I'd add a few resources.

I've been using Tineye, Google's Search By Images function, Bing Visual Search, Pixsy, and Lenstracer. Tineye used to do a good job of finding images but now it's finding a lot of dead 404 pages. Google Images search works very well at finding active matches. Bing finds something occasionally. Pixsy searches multiple images simultaneously and works well but also finds a lot of false positives and dead 404s. I just started using Lenstracer and it also searches multiple photos simultaneously and has had good results with fewer false positives. Hope this helps.