I like it a lot, i think the darkness is spot on - really gives a horror vibe. Maybe lat the playable character have a torch (and then at the most inopportune time the batteries can run out - cue the chilling music)
What about some dripping water coming from leaky pipes? Or even a red gas line that is running in the sewer, maybe with some leaks in it. I feel there should be some element that pops (but in a dark way) so offset the overall brown’ness
Great additional effect to a map like this is the sound of something swimming through water like a fish in the sea type sound. But you never seem to see anything. Adds a great Horror effect in a dark sewer map like this.
Yeah I think one thing that stands out to me is that with that many lights the brightness you have on them the falloff is too short - you either need to dim them a lot more so the light on the walls are not so bright. I would at least double the radius and reduce the brightness to maybe 0.2 At the moment because they are so bright it feels fake / off because the centre of your area is almost pitch black. Hope that helps