I also want to know that. I had my service on my own website, does eBay allow to watermark my ads image with my website url as watermark?
At first I was not water marking my pictures. Several of my pictures I took by myself with my digital camera. It takes time to take product pictures. But after few days i saw another guy stole my picture and listed on his listing. It didn’t look me nice, so I contacted with that person and requested him to remove that picture and he did. After that i put my username on the picture as watermark only on those pictures that i have taken by myself, and if the product is not a used product and i suspect someone else can steal it. I use skydx.com to host and watermark my pictures.
I was selling diamonds and jewelery on ebay and all my images in the listings were clicked by one of my professional employee, hired by me. However after couple of months, I realized that all the images which we had taken for our products were copied as it is by doing some work in the photoshop. Since then we started posting our company name as the watermarks in all the images. However you dont have to display the watermark, it should be blur so no one can see it at the first place and if they copy we can claim for compensation
You can watermark your pics but only if you are worried about someone stealing your photos for their own use. If you don't care about that it doesn't matter.