Back on topic. We've spoken about this before but I think it's worth reiterating, I think you need an outline design document. Doesn't have to be war an peace.
At this point you're the only one who can say if the scene itself is straying too far from the rest of the body of work as only you, at this time know, or at least should know the overall structure of the work. If you don't then do the thinking before you start on screen.
Either there is a coherent narrative or you have a series of loosely connected scenes where you shoot some zombies. Both are fine if it's the former then you should have an outline story that shows how you go from point A to point B (i.e the urban to rural settings). If it's the latter then you can be as abstract as you want, you could shoot zombies in space.
I personally prefer some linear structure to a game.
As for the quality of this particular scene, you use some nice looking imaginary in some of your work so you must see that this looks shoddy. To me it looks like an early storyboard or something a young child brings home from school. Sorry if that sounds harsh, but I agree with Cyrano on this point, that really shouldn't need pointing out. I think you can be hyper real, hyper abstract, cartoony, purposefully shoddy (yes that can sometimes work) but the style should be consistent and in this case you've gone from one beautiful background hyper real background to some kind of fake composite.