Far from the horror-show dungeon that it is often portrayed as, the Tower was (and is) a fully-functioning miniature city. 

Even at its darkest, the prisoners kept there were nobility, and were, for the most part, afforded a lifestyle that commoners living in East End only a quarter of a mile away couldn't have dreamed of. 

While acknowledging that part of the Tower was a prison, and even a torture chamber, the folks who run it strongly emphasize that it was (and is) also a military garrison, a home to soldiers, politicians, and clergy, and a seat of political power. 

The taking of pictures is not allowed inside any of the tower buildings, unfortunately.