I see a lot of art playing with religious motifs when it comes to depicting Kankri and The Signless. I think in terms of symbolism that art is rad, and gorgeous. However people should not take the abundance of religious imagery in Vantas fanart to be canon indicators of the Vantas personality.
The only troll religions spoken of in the comic, were the Church of the Mirthful Messiahs, and the Cult of The Signless.
The Cult occurred after The Signless was horribly martyred, and it was a zealous reconstruction of his ideals militarized for violent revolution. The Signless didn’t live to be constered into some sort of prophet, his emphasis was that he was an equal to all trolls, as all trolls were an equal to him. He would not have wanted to be a religious figure.
Kankri may be preachy, holier-than-thou and self righteous, but none of that makes him religious in canon. His derision for all that the Cult of The Signless did to warp The Signless’ message is evident in his mocking use of 6’s and 9’s in his quirk. He mocks the shape of the shackles that the Cult worshipped. He doesn’t agree with the religion surrounding The Signless.
Karkat wears the symbol of The Signless’ shackles unknowingly on his shirt from childhood. He finds Gamzee’s devotion to the freaky clown cult weird, and generally seems ambivalent towards religion. But he does call himself a God. So you know, you can go nuts with the religious symbolism for Karkat. It would probably feed his hungry little ego.