You might benefit from some gradients. Your flats are fine, but this is just a nit pick... just that one little thing to help push the art a bit. On your backgrounds/things that aren't as important as your figures, keep lighter and add a gradient. It will help to separate your figures more.
Black and white comics also tend to look best with some line variation. It's what separates the beginners from the pros. Think about practicing some brush pen/ink stroke stroke if you want to give your comic a more polished feel.
Otherwise, I enjoyed reading your story. The paneling is simple but very easy to follow ( simple isn't bad lol ).