The quality and creation date are good ways to identify traced picture from original. (Obviously the traced picture is always done after the original, and most likely has much lower quality). Its also good to notice if the copier of the picture has given credit to original artist. That makes the picture fan art.
I am not artist, but I think I understand how this system works. Correct me if I am wrong.
I like this picture. It could make nice poster, I think.