Sam knows that these photos are important to Dean. But they’re also important to Sam. He found them in Dean’s bedroom when things were at their worst: when Dean was locked in their dungeon black-eyed and shouting abuse. He took them off the bonfire that the Stynes had made and he kept them beside him to remind him why he had to act. He carried them in the inside pocket of his jacket. And he gave them back to Dean, at what he thought was the end.