Some people are saying that the images in the mirrors are the places where Jacob touched the candidates (which shows some inconsistencies because the hospital is where Jack was touched. I think there is actually more meaningbehind these locations. The mirror shows the place where the candidates derived their identity.
James Ford's desire for revenge after injustice led him to create his identity as Sawyer at that church, when he decided to write the letter.Sun and Jin gained their identity as the Kwon's (which is what most matters for them as characters) at the pagoda when they got married.
In the same way, this could be the writers showing that, above savior and good doctor, Jack's identity is that of lost, orphaned child. He was orphaned by his unavailable dad in his youth, his perceived meaning of life, and any attempt at a loving relationship. Before Jack can truly earn his identity as the savior and healer of the island, Jacob needs Jack to let go of his orphaned soul. That's how he can heal himself.