The very unhappy, even angry, face of Peter - totally out of keeping with iconic painting, tells quite a story - as he literally glares across the Lord at James.
In addition, Jesus and James are dressed identically - another pointed message. Their hair is the same - the way the Nazarite Sect wore their hair - and if you looked at James and 'turned' his face towards you, it would be the spitting image of Jesus - this is testifying, in code, that James is the BLOOD brother of Jesus - something the RC would be very upset about someone claiming, as the church, in the Nicea Council, 325 after Jesus, declared Mary never had any more children - ie, no blood line to threaten the authority of the RC claim of apostolic succession and right to rule....
Jesus is holding a message that says "I am the Light" 0 perhaps the artists 'code' to signify there is a message in this painting beyond what most people 'see' when they look at it...
I have seen hundreds of iconic paintings and can't recall one other one that departs from the formula of bland, unemotional expressions. Peter (representing the RC)is pis*ed!