In the prison cell area, maybe you could change the colour of the fluorescent lights to something a bit more blue-ish to make it look colder. You can then also use neutral or warm lights to highlight areas of interest.
And I'm a bit bothered by the looks of that wall between the locker rooms. It looks like it was built that way instead of having partially collapsed. (If it was built that way, which would be very plausible, I would advise using modular wall panels instead of bricks, since it doesn't need to provide any structural support.)
BTW the turrets look neat with those coloured stripes 






