I can tell that you have what I call a steady hand. If I were you, I'd try to spend a lot of time on just one picture. Doing this could get you really big results.
From what I see, it looks like you have some potential, but you're just using it up on smaller and less detailed drawings. I bet that if you were to spend around 3 to 4 hours on one drawing, you could probably create something quite nice. I would say aim big, because simple doodles are all over the place in this forum. If you want to stand out, you need something that's better.
I'm telling you this because it looks to me like you can pull it off if you really give it a try. Anyways, keep the practicing up!