Clicking the larger image would be acceptable - though a button would probably be easier to understand (for the shopper that is).
P7 has a tweak that enables linking from the larger image seen here… answers.asp?id=231
It would not be a problem for me to regenerate the larger images to include a button as part of the image.
All of which is to say - I'm flexible.
As long as the end result is a trip to Product_Detail.php where I can add options of size, paper type, framing etc.
PS. Where is the server that handles these posts? I just noticed that the time imposed is 4 hours East of me which would put it somewhere west of England!?