some tips :
- no stars, city lights oppress them
- colorful lights, city lights are never white
- if you don't have secondary light source, the shadows should be extremely dark ( I put some glowing circuit there to fill the empty parts with interesting details)
- bounce light from the face should paint reflection on the window ( my example is not accurate, I just copied the face, you should draw a mirrored version lit up by light)
I hope this helps, dont be afraid of using dark values, and get references for everythig