Kat: Use tineye.com to reverse image search. You can upload images directly or link to the image wherever you found it, and it can find the oldest version online most of the time. It's not infallible, but it is certainly a start if you're trying to find the original artist of an image.

Personally, I use whatever images I can find when it comes to character images for roleplay. I do make a point of leaving watermarks and signatures alone and I never alter art unless it is to crop it. I also leave pictures alone if I see that they are marked not to be used. So, yeah, that's where I draw my lines at. I figure, leaving watermarks and signatures alone might possibly bring the original artist more traffic by using their art as a reference, and that can't hurt any. I also think it would be insulting if someone edited out a signature, watermark, or any other sort of editing aside from cropping and resizing (I hate it when I see obviously photoshopped art because someone wanted the hair color to match their character. It has to be insulting, like basically saying what the artist did was not good enough). I also like using dollmakers, as there are some really good ones out there that the artists and programmers of them have stated they can be used any way you want so long as it isn't for profit.