Illustration refining / development

I've been spending some time trying to refine the first illustration in the book. It's supposed to be the outside of the cafe where the first scene takes place. It's night time (3am), so it is dark but the cafe is still fairly busy. The rest of the street is supposed to be empty/closed for the night. 

After spending a long time drawing the scene out, I roughly placed some colour values. This was so that I could figure out the depth of the scene and where the light sources would be coming from. It was like an additional sketch layer for reference.

Then I placed the main colours that I wanted in the illustration.. but at this point the whole thing felt flat and the colours didn't really harmonise with each other. I thought it would be fun to explore how much I could change the colours but still ensure the main building still read as green.

I was a bit happier with this version. I've added some depth/shadows and boosted some of the light sources. I felt it could be even more harmonious though..

Here I overlayed a gradient mapped version of the illustration. This boosted the contrast and pulled the green back so that it suited the night time scene more.

There are some details I want to go back in and add - such as the sign and name of the cafe (once I have finalised that) and perhaps some details like cobbles on the road.

This has taken me much longer than I anticipated. This is because I'm experimenting with a new digital process and allowing myself to explore as the illustration develops. This means that my outlined 8 illustrations may take a lot longer than I had originally anticipated. In addition to this, I have also started to consider whether I could add in more sequential illustrations to the novel. I'm unsure whether these static 8 illustrations are the best option. I think I'd like to explore the writing in more of a comic style too.