LOL - yeah, the day anyone gets the pirates by the throat then wake me up.... It will just change. They would just XOR the image with another standard template file and post that instead. Casual reposters - yeah, pirates - no way. Its a good resource so thanks for posting but lets not get overly excited about its potential to find knowingly ripped stuff. Its a useful tool in the box to search with.

Google images has a search by exact size. Now I am a bit of a nerd so all my images are 1024x768 or 1280 or 2048 etc but I just did a search for a common topic but with exact size match to something bizarre and it gave back just 5 images. So my advice is just make your map an odd but sensible size that no one would be bothered to resample and then google is likely to index it by size and you may have a better shot at getting a match on it even it was renamed to something unsearchable from the original name.