The artwork that you've done for this game is extremely nice, each of the timelapses you posted to the AGDG threads also shows just how much effort you've poured into it. I must say some of it looks slightly off with the scaling/line thickness, for example the map terrain has really thick lines but your base vehicle has much thinner and refined lines, kind of making it look odd. The backgrounds in some of the scenes and some of the character sprites could also be slightly more differentiated I think, like you could lighten the outlines of backgrounds a bit and add more edge highlight to the characters to have them stand out more.
That said, I really like the characters you've got so far. I didn't have time to get to the end unfortunately, but I enjoy your writing style and the overall story and concept a lot.