Loving those roof tiles! Hmm, maybe you could do some fake transparency on that wall shadow? Recreating the floor tile with darker colors similiar to how you did the light effect on them. I would say, take the floor lights down by 1 notch on your blue palette, so the lightest blue now becomes the second lightest blue only across all colors.
The sprite is pretty bright, but he almost looks like a ghost. Need to get some color back in there. As for the perspective you basically have 2 choices, dark floors, lighter walls, or vice versa. It can work either way as long as you control the layers of importance so the player isn't visually distracted. Right now if you try to focus on the sprite, your eye wants to jump to the floor lights because it has more color and is brighter.
Let's see those people in tanks, and maybe some HR Giger inspired tiles. Maybe some wires curling around the floor too.