I recently ran into an issue with a CH who decided he would just grab the .jpeg file from the page that opens up when you click on a thumbnail. He is now using my logo even though he has not compensated me.

This is as easy as using the Selection tool in Photoshop (or similar application) to extract the design from an entry. To protect your designers you need to make it impossible to grab ANY image from your website. Perhaps when the designs are displayed, you could make them a background image that can't easily be dragged and dropped onto ones desktop, or perhaps there is some other code that locks a design in place. I can't imagine that this is the first time this has happened. While you get paid by the CH, your designers get burned and their artwork stolen. This is a BIG problem.

DO MORE TO PROTECT YOUR DESIGNERS SUBMITTED WORK!!