one cap, one comment
Very strong image - Sam crucifed, upside down, over a devil's trap.
An inverted crucixion is strongly associated with Satanism - the worship of Lucifer - so the message here is one of Sam's alliance with Hell. This image comes afetr Sam has imagined himself being tortured by Alistair. I felt there was a progression in his halluciantions - he starts off struggling with this path he has taken - Sam (the human part) is tortured by the demon part of himself. Through the subsequent hallucinations he works through this struggle to believing he is doing the right thing (via his internalised maternal figure) and accepting the cost (being a monster and losing Dean).
There is another meaning here too. The inverted cross is also know as the Peterine Cross in Roman Catholicism. Peter, one of Jesus' disciples and foudners of the Christian church, was killed for his beliefs by the Emperor Nero. He asked to be crucifed upside down, as he felt unworthy to die the same way as Christ.
I feel Sam does see himself as a martyr - he is willing to give up his humanity, his life, to kill Lilith. Interestingly, in the light of Sam and Dean's estrangement and Sam's - "You don't know me..." - Peter was the disciple who, as foretold by Jesus, denied knowing Jesus three times on the night of his arrest.