Hi mapper, I have a little to tell you about the map:
First, using few textures for a large map made players "stuck". It's hard to see the way. So please use more textures or change these to dev texture. Don't forget to use texture scale and texture shift option to make it detailed and hi-quality.
Next is about lights. You should add light for map. Most basic is light entity. You can learn about spot light and dynamic light for indoor map. This will help render and shadow for map. That's good
Most important part for indoor maps (or even outdoor maps) is cubemap. once you have light on, add cubemaps. To know clearly about cubemaps, take a look here:
Good luck and happy mapping