I was going to say that if you name your images something other than the product name, it makes it harder for people to pull images from a google image search, seeing as your images wouldn't show up if someone searched for "Celtic Knot Ear Rings" (just as an example)
but you've done that already, you've named the images as the product model and not the name, so its doubtful they got the images from google, more likely they've swiped them straight off your site
I've had people use my images before, they didn't even copy the image, they just used the image url straight off my site, not only stealing my images but using my feckin bandwidth aswell!!
easily fixed though, I just changed the image to something rather distasteful, so instead of a nice clean product image showing in their ebay listing they got something slightly more shocking

well if they have the cheek to use my images and waste my bandwidth, fair's fair
