FIrst I was going to say your perspective was wrong, but after a quick paint over it seems that the only lines that son't match a vanishing point are the lines on the roof nightingale stands on, the mid section of the roof on the left and the window on the foreground... No big deal, and it's only the first one that gave me the hint.
As for color, you seem to really be straying out of your comfort zone, which proves once again your courage and determination. But for now it feels kinda clumsy, at least for the buildings treatment (the work on your character however is really nice and subtle).
Also, I'm not very fond of the little strokes you put here and there on the roof. They're either too shy or too present. It's okay to have empty areas, it balances the composition. You really don't need details all over.
It might not fit your bill, but look at the work of Mike Mignola, especially how he works with black and solid colours or subtle shaded tone (well, he has someone doing his colours after a few hellboys, but still) and how he uses very few details.
I'm surprised that my perspective was ok, I eyeballed the whole thing and used no rulers. XD
While I worked on it, I wasn't sure if I wanted it to be more of a composition with overlapping elements that aren't necessarily in the same plane (as people often do on comic covers) or if I wanted it to actually be all one plane. It would never be possible to have the Central Station there, because there is no building like the one she is placed on in front of it like that. I guess my indecision is what led to that slight incongruence. The main background was an afterthought.
I know what you mean about the strokes too, I'm just starting now to try to emulate Florent Maudoux's style, and I'm still struggling with the lineart. I'm very used to Sister Claire and super stylized lines, so getting into this more realistic stuff is forcing me to use another part of my brain. XD; I'm going to keep experimenting with it.
I'm not sure Mignola is anywhere near the sort of style I'm aiming for here. He's a bit too simplistic for what I have in mind, but I know his black placement is still something to learn from. Thanks for the long critique.
As for Mignola as an example, it's essentially because I have a fondness for clean black masses. Why I thought it would fit with your style is because you're oding very well with simple designs, and working halfway between your work on sister Claire and your Nightingale project could work well with this kind of treatment.