the ground looks way too flat. it should be slightly higher and slightly lower in different places. and you might put some 1x1 flats around the place as rocks. also, dirt grounds are just pretty ugly in general. i guess it fits the theme but i always prefer grass.
the tents should have supports through the middle, and they should have inverted ramps on the inside walls, so they look like / \ that instead of being super blocky.
that wall looks pretty weird. pure white material seems like a strange thing for a post apocalypse society to be building with. i think just a gray fence with red/grey bricks at the base would look better.
the trees are too uniform. usually where trees grow, there is also grass too. they should be spread out all over the place. its weird for there to be no trees and then some super densely packed trees in one spot.
the area walls mostly look good, but i would recommend you make each later at least 1 brick back from the layer below it, so it doesn't look like spam. it will feel like real terrain. also, you might want to use modter for that, as you can texture it.
here's an example of a post apocalypse (kinda) area that me and magus and conan did. the materials are dark copper and iron, which makes sense. also the floor isn't flat, and the area walls are different after each layer. they wouldn't look nearly as good if we just duplicated the second layer all the way to the top.
