I actually liked the shadows, to be honest.
I think some lighting won't really hurt... or maybe some baked ambient occlusion.
I'm just not a big fan of this look where all the walls have the same brightness. It kind of takes away that 3d-effect.
Thank you for your reply man. Please take a look at this video, I'm just playing around with 'fog_end' value:
GAME_PROGRESS_WIP_02 Edit: yes, I know that it's too 'dark' actually I'll increase 'fog_end' value, made this video to show the basic concept.
Greets!