Art historian's comments below remind me of how Our Lady of Guadlupe was painted by God:
For his part, Casper has studied devotional manuals, sermons, and other printed texts that focus on the shroud from the 1500s and 1600s, the period of the 14-foot linen sheet’s most heightened and unprecedented devotional enthusiasm.
According to Casper, no one at that time thought of the shroud as a painting per se. “They didn’t regard it the same way they did Michelangelo’s painting on the ceiling of the Sistine Chapel, for example,” he says.
But the printed literature does refer to the shroud metaphorically as a painting made by God, whose brush was Christ’s body and whose pigment was Christ’s blood. Casper says these ways of discussing the shroud reveal a different conception of artifice and authenticity, which today we often perceive as binary opposites.
Contrary to what one might expect in modern times, metaphorical comparisons to art in the 16th and 17th centuries bolstered rather than undermined the shroud’s authenticity.
“There was a reverence at the time for artifice,” Casper says, “and the shroud was, in a certain way, an artistic relic that for contemporary believers gave evidence of God’s creative powers as artist.”