When it comes to safe guarding your image from some ass'hat, sadly there is really nothing you can do.
While Mel, I or anyone else does our best to watermark our "work" there are so many people out there who can easily remove it with a bit of time on their hands. Yes, people are that desperate.
Does it peeve me off? Of course. But if I managed to track someone down who does use my work or anyone else I know, all I or anyone can do is send them a message and inform them to give credit where it should be. Even then these ass'hats generally laugh and ignore.
Its difficult for me to still accept of how society has become so rude over the past decade. Use to be go into a store and say "Excuse me" and someone would say, "Oh, sorry" and move. These days I do it and the person does not move nor say word. Its like manners have completely been blown out of some peoples lives and into outer space. And the internet is far far worse. Sometimes it can get so bad its like flashbacks to high school days.
While we can do our best to ask for credit in the end people do not care and that angers me just as badly as someone "thieving" our work.