I've been in your position before, having a scam accusation posted up against me, so I won't try retaliating against any of your comments.

In response to your copyrighted material claim, I would emphasize the fact that my work is not, in any way, another person's property. It was an original card created by me.

Therefore if you claim that it is copyrighted and you have no proof of such, you have no reason to refuse payment. If you find my work on any other website though, please send it to me so that I can have it(the website) taken down.

When hosting a contest, you are liable to choose at least one winner. It was a waste of time on our part that you have suspended the contest two months after we delivered our work.

EDIT: I do not require you to pay me, but I am willing to drop charges if every other designer in the contest agrees so.