JB posted a vid of himself walking around his home Saturday morning -- shirtless, of course -- showing off a shocking amount of tattoos on his torso. Seriously, his entire upper body is now almost completely covered in tats.

It looks like the fresh art on Bieber's midsection has a religious theme -- including archways and angels -- which would be in line with his new look on life.

As you can see ... last time we saw the Biebs without his shirt on, he was not nearly as blasted.