It's because of nonsense like this that I stay as far away from these sites as possible. I am extremely adverse to non-custom graphics.
I had to use a paid image recently for a website, and I bought the rights to the image. But now I have to keep it somewhere that I can track it for the next decade in case these people decide to fire off a C&D.
Far better to find an inexpensive artist and pay them. It's surprisingly inexpensive. I just called a local fellow, he wants $30/hour and he does some of the best custom illustrations I've seen on the web. For a few hundred bucks I end up with illustrations that look magazine quality (not the normal bought crap). And I own the copyright.