That's a new word I've just invented (in fact, a borrowing from French). The adjective Christic (distinct from Christian, but clearly inspired by the same personage) simply means "related to Christ". Here's a Christic explanation of the creation of the US Constitution in 1787:
Painted by a certain Jon McNaughton [website], this allegory strikes me as the pure expression of a grave form of Christic insanity that may (or may not… I don't know) be endemic in parts of the USA. To call a spade a spade, I believe that people who need or admire such an image, not to mention the individuals who actually produce and market such shit, are suffering from some kind of brain damage.