The best explanation I've seen of the Shroud is that it's not a two dimensional "illustration" at all. Instead, it's a two-dimensional image created from a three-dimensional process -- much like an X-ray or MRI. This would mean that the image was created through some kind of supernatural -- or even totally "natural" from the standpoint of physics -- event that cannot be replicated even by the top scientists in the world today.
By all accounts, that event in question was the resurrection of a human being.
Certainly there were artists in the days of Jesus ... no one thought to draw a sketch?
Granted, there are a lot of things we don't know, but there are a lot of things we DO know, and no longer look through a glass darkly.