When I first saw this map I instantly thought Halo 2 mission Delta Halo. Same lighting and texture.

 

It looks really nice aesthetically. I think, by looking at the pictures, you could add some covers. I'll give you some ideas :

http://www.forgehub.com/attachments/image-7-jpg.22730/

There, you could delete one column and create 2 or 3 blocks to create some little cover, and create a "story" for the map, as if the column you deleted fell.
It could create a variation in the set of the place, and in the gameplay.

Another thing : Add some trees ! It gives a really nice effect of natural environment and cool lighting/shadow effects. It could also add covers to strategical places, or maybe just a better aesthetic to the map.

http://www.forgehub.com/attachments/image-4-jpg.22731/

This place... Do we die if we fall in the hole ? If yes, you could create something cool : Add several columns made of rocks (natural elements) to allow Spartans to use their new abilities (sprint, climb, dash etc...). By adding these elements, you allow players to do more things on the map, by using more ways to go somewhere and therefore : you create a smoother gameplay.