Regarding the photo library, I can speak for my wife. We have a kindergartener and one of my wife's favorite activities is to watch pictures / videos of our kid in bed. She can do this for hours on end to entertain herself.

She also likes to watch movies on an iphone instead of a big screen cause she can use it while performing other tasks (cooking, cleaning etc). She has always said no to a larger form factor like a iPad but I think this might be a good use case for her.