There is a hidden face tucked in between the arm of the Priest featured in Banksy's Concrete Confessional.
The face was not clear during the day, but became apparent at night time when using a camera flash. The face seems to be applied by a misted layer of white shadowing on top of the black. This is also not the first time that Banksy has included subtle subliminal messaging in New York.
Love how the hidden face contributes to the content, as if the hidden face represents the demons that are haunting the Priest.
This is fucking awesome! Incredible technique displayed on an already awesome piece.