Also, I don’t think anyone disputes that the Shroud is unique . . . However, the fact that there are no other comparable 13th century images can be contrasted with the fact that there are no other comparable 1st century images either. Uniqueness by itself is no proof of anything.
True. But if it is not unique; then what?
I think it is significant that the shroud is unique, which, of course, cannot be proven.
For Christianity, apart from whatever we may think about the shroud, the claim of something being unique plays an important role in belief. The Nicene Creed is an example. Try to imagine it as a set of not-so-unique proclamations.