Why would being resurrected make an image on the shroud anyway?
What the Resurrection did is twofold:
1) interrupt the process, so that any further degradation of the body which *would* have happened (together with any effects this would have on the shroud) was arrested. This meant that we had a snapshot in time of the chemical reactions between the body and the shroud.
2) leave an empty shroud around with an image on it, so that people might happen to notice.
It is important to note that we don't knwo the exact conditions under which the image was formed: temperature, humditiy, any spices or such used to prepare the body; the exact duration between time of death and burial; and the condition of the body when placed in the shroud (e.g. beating, possible dehydration, crucifixion, etc.) -- all of which might have effects on the condition of the body. (Bruising and rupturing of cells will leak the contents of the cells outside of the cell walls) -- which might affect the rate of decay or the relative composition of any decay prodcuts initially.)
It is also important to note that if the shroud is really of a crucified man, theft of the body (as alleged in atheist schlock book "The Passover Plot") would interrupt the process as surely as a Resurrection.
So accepting a 1st-century provenance for the shroud, and even accepting that the man whose image is on the shroud was crucified, does not disqualify any other suggestions about the shroud due to "superstitious nonsense about the Resurrection."
Cheers!