WoW, you really analyzed those screenshots ;)
1: In the campaign, the base you see in picture 2 and 3 is a newly established military outpost on top of a civilian facility (this is where the player starts). I suppose I put the sandbags there to protect the turrets and didn't find anything better for it.
Picture 1 is another part of the map and is supposed to be pretty run down and not cared for. I guess I didn't think about the vines being illogical ;)
2: You are right, now that I look at that part more closely. That gas station could look much more realistic.
Thanks for the feedback! I made this map more than 2 years ago, although I haven't shared it before publicly since I never finished it. It's actually quite large, so if someone would like to have a closer look at it, I could send it through pm.