I'm with Kris - having it cover the entire background is a bit confusing. Remember - most customers don't really take the time to actually *read* the description so even though you explain that the watermark isn't in the actual print, most people will just look at the image and move on.
One idea to protect your image is to include just one watermark (transparent overlay on top of or around the image) and then use one of your 5 photos to show an image of your print in a frame (mentioning that the frame is not included in the listing) so they can see the quality of the print in a "home - like" setting without the watermark. This helps customers envision what the item would look like in their own home and further discourages unauthorized use.
