Your stuff is boring.
It's like a plan. I as no life, no fanzyness. If it's gray, you draw it gray. If it's blue, you draw it blue. That's not art. Art is drawing beautifull things. Things that are fun to watch.
Ok, so if ypou belive I'm right, here what you can do to make this pixel ART.
First, define a light source. This will give you an ambiance you can play with.
Second, change those borring colors into cool ones. A simple way to do this: Your shadow should not be only the same color with less light. It should be the same color with a blue tone, or less saturation.
Third, MAKE IT DYNAMIC! An other view angle could help. But moslty, there is nothing going on in your drawings. BAM! The train exploded! Something intersting.
Here's a quick rough to show you what I mean: