Well, I don't think that people use 3d software for their first game, and as I understand this is your first one.
I started to use 3d only after my first couple of games, my first screens were also simple drawings
Yes, you have done a good job. Your screens show a certain atmosphere.
I like the scene with the bridge, the close-up of the huge buildings, and also the destroyed building is good drawn in my opinion.
Did you use Paint or another software?
Just an idea: Maybe you could add some more details to the "international city", it looks a bit empty.