Send a message to the person who requested a photo of the grave monument of William Stoneman with the following comment:
Hi, I'm currently researching the Stoneman family from Kingsbridge on behalf of a client (I run a small genealogy business) and believe that the William Stoneman memorialised in this image belongs to this family. I would love to add this image to the research (provided I have your permission of course) - I would be very happy to credit your website in the research. I'm only a small business, and so unfortunately cannot afford to pay you for this, but would be more than willing to help with indexing etc. should you want me to. Yours, Cerys