I'm still working on my props that I hope to put up sale. And I was thinking about using parts of some images that are on a classical art website as bump maps (after I modify them in PS of course). Now, even though these images will be greatly altered, and then applied to a wood or stone surface so that they will be almost unrecognizable, I still thought it proper to ask the people at the site for permission. Unfortunately, repeated emails have gone unanswered. Would it be ok for me to take this non-response as consent, and proceed with making the props?