this is a simple job either to water mark all product images in [url removed, login to view] manually, or to use a script such as [url removed, login to view] to automatically watermark all product images. personally i prefer the second option if executed well. i am not sure if the plugin in the link above work so its your job to provide a solution.
my goal is to protect product images to the maximum. give other solutions if you have. happy bidding.