Hey it's not
that far out there...
I did a little digging and found that there is a 'diptych', (a two- piece hinged picture... who knew?) from the 10th century portraying "Abgar V, Ruler of Edessa" holding a cloth with an obvious image of Christ on it. So there!

Also, I did some digging into your claim that an artist admitted to painting the image on the Shroud;
It seems there
was a memorandum written by a Pierre d'Arcis claiming that an artist had admitted painting the image, however there are some problems with the story:
d'Arcis claimed that it was actually his
predecessor, bishop Henri de Poitiers of Troye, who actually held the inquest, although there are no records of such an inquest. Strangely enough, after this 'inquest' was held, the 'artist' was never even named... what was the point?
Also, the memorandum exists only in unsigned , undated copies. There is no evidence that it was ever sent to Clement or recieved by the Vatican, as no copies of the signed memorandum exist there. So the "admitted artist" hypothesis is somewhat doubtful it would seem...
Check both of these items out at
http://www.factsplusfacts.com "Edessa to Turin" and "D'Arcis Memorandum"
The "Open Letter to John Dominic Crossan" is also very informative!