I understand that someone might use the image to put up a 
false auction, but they could do that with anything. They
aren't taking anything that you created yourself. If it was your own creation,
then that WOULD be wrong. Even the "fair use" law allows
for people to use copyrighted items as long as they don't 
profit from it.

Now if someone is using your cel images to create a false  collection that
they claim to own, that is more of a personal problem than a legal one. Just my 2 cents.

P.S. That letter was pretty snotty though.