Hard to say smth.
Your drawing are "flat". It's not wrong - but in my opinion You should to experiment with Your unique own style. Very interesting drawings with very poor using of shadows and lights have japaneese authors. Drawings made by them are like sketches.
So I mean maybe You should work with different kind: of lines (thin, kind etc), weathering and using at very minor spectrum lights/shadows.
Try to find gawings e.g. Kow Yokoyama - he is really master at that.