Normally when you hear the words "hack" and "copyprotection" together in a sentence, you think of something that removes the protection. But I've discovered a hack that does the very opposite. It will actually ADD COPYPROTECTION to a picture. If you don't want someone creating a derivative work from your artwork, I found a way that is a sort of hack to keep Photoshop from even being able to load the image. It's a special watermark, that causes Photoshop to REFUSE to load the image.
Check out the below demonstration image. If you try to load it into Photoshop, or even load it into MS Paint and then copy/paste it into Photoshop, Photoshop will REFUSE to accept the image! (note, it may not work as intended on versions of PS prior to CS)