Though chemical agents, such as acids, could alter the chemistry of the fiber, the lack of any capillary action and the abrupt delineation between image and non-image areas in individual fibers preclude this as a reasonable possibility. The image is a 3-dimensional map in negative. This is totally uncharacteristic of any art form. Areas that are recessed such as the back of the knees would have required few or no pixels. The image is anatomically consistent, to a modern day pathologist with 20th and 21st century technology, with someone who had been traumatized by scouring, wounded in the scalp as if by a cap or crown of thorns, and crucified.
Death seems to have been by asphyxiation which is probable.
The blood stains showing both artery and vein flow are pathologically correct. No medieval or pre-medieval artist would have had the knowledge to create such an image. The image does not exist below blood stains. An artist would have needed to apply real blood first anticipating the exact placement of the image or to have created the image with reserved areas for the blood stains. The very idea of an artist doing so is preposterous.