What do they pictures exactly reveal?

I think the pictures make her remember what she had lost sight of, because of the grief, pain and anger. She was shocked to realise she couldn't answer the midwife's lawyer's questions about what her daughter looked or felt like. The picture gradually develops as she slowly remembers the brief period of joy she experienced with her daughter and her husband, and the part the midwife played in making this possible. The rest, I think, is made clear in her address to the court.

https://www.youtube.com/watch?v=AbVIgPHablE

It's a riff on a scene from Sydney Lumet's 1982 film 'The Verdict', where Paul Newman, an alcoholic, washed-out ambulance chasing attorney goes to visit a "client" at the hospital (a young woman who also lost her baby due to malpractice and is in a permanent vegetative state, plugged to an artificial respirator) to take polaroid pictures of her in order to pressure the defendants into an out of court settlement and avoid going to trial against a private hospital with high priced lawyers.

As the pictures develop and the image of the bed ridden comatose young woman in fetal position gradually appears on screen, he begins to "see" her as a real human being instead of his meal ticket, and remembers what he used to stand for. He decides to go to trial, and give her and her lost child justice.

It's an extraordinary sequence in a fantastic film from a great director. Check it out if you can.