Serpent iconography isn't inherently evil. The ouroboros for example, or the rod of Asclepius are common and acceptable. A snake is generally a symbol of rebirth since it sheds its skin. It's strange to see it in the Pope's audience chamber, as I'm sure it represents Lucifer but even then without Lucifer there'd be no need for the church. That doesn't change the fact that the catholic church is run by baby rapers and boy lovers.