The listing has a "Report this item to etsy" link at the bottom. I think there's a "my intellectual property" choice. You can also email etsy about it (contact is through the Help link at the top of the page).
I've had images stolen from another website I run off etsy. When I reported listings using my images (digital collage sheets), they were usually removed within 12-24 hours. Hopefully you will have the same luck.
Etsy may ask you to jump through some hoops to get the offending material removed. If it looks a bit complicated, it's because it's a legal process. If you can show Etsy that you had the material first, Etsy is *required* to take it down.