Early Church Icons and how they might have been influenced by the Shroud.
See "Iconography"

Dr Alan and Mary Whanger have done excellent research comparing the Shroud image to ancient icons and coin images and developed a technique called polarized image overlay that compares the points of congruence between them. The exercise demonstrates that the Shroud most likely was the object being copied all the way back to the 6th century. Read about their work at http://www.duke.edu/~jcp2/shroud

The following is a good primer on how Icons were prepared and how they developed as a spiritual discipline. After Constantine legitimized Christianity, Icons became a visual theology beginning in the 4th century. http://www.iconarts.com/originstechnique.html

Another view of iconography is that it supports the thesis that the Shroud was created as an icon in the 13th century. The following article from Nicholas Allen contains certain inaccuracies but nonetheless provides an interesting backdrop to the role of icons and art during the middle ages. However, the article assumes the carbon dating to be accurate which now has been proven to be erroneous. In addition it offers no explanation as to how the image was created. Although the Shroud image may have certain similarities to medieval icons, the differences from both the standpoint of art and science are enormous. Mr. Allen believes the Shroud image was made by a primitive camera projecting the image of an actual corpse onto the Shroud over the course of several days. So in fariness, here is a contrary view.

http://www.petech.ac.za/Shroud/Dating.htm