Do you have a supplier? You can ask for the supplier's permission to use their images.

You can also use inspector tools in Google Chrome to check for images that do not have watermark.

Yeah, YourGoToWriter's right. You can go to your supplier for high quality images. Not so sure about inspector tools, but hey, might as well give it a shot, right?

Make sure the images really focus on the product--good lighting, different angles, no distracting backgrounds. If you want to put text, be straight to the point. Give the benifits. Make your letters bold.

You could hire a photoeditor for cheap if you have to go through a lot of images but don't have the time for it. (try Filipinos--very inexpensive, but the good ones work their tails off.)