Need opinions -or what would you do?

Remember my set of The Angels? Well if not dont worry. But a couple of absolute Die hard Fans contacted me and asked if they could buy some photos.
My question is Do I leave a small watermark in the corner as a signiture or dont print it at all? I figured that it is a piece of art so therefore like an artist who has created a painting, he would sign his art work.

What are your thoughts??