very nice job--good for you!
To improve it you might consider:
Create more dynamic lines by varying your line weight a bit more. This variety in the line will give the drawing sense of movement, that's huge. Being conscious of this will also help you practice your draftsmanship
It can also create depth. For example thick, dark lines will appear to advance toward the viewer while thin, light lines appear to recede. Good stuff!
Think of where the light source is. Is it camera right or left? Above or below? Once you establish this it's easier to design both the shadow and light patterns. Just think it through logically about what will catch the light and what will be blocked from the light. I know you can do it
The lighting will give your drawing a feeling of solidity as well as a sense of drama, reality and depth.
Hint at the background with some value or use a graphic shape filled with a dark value to frame the character. This helps eliminate the floating in isolation look that many drawing suffer from. It also tells the viewer where to look by calling attention to it with value contrast.
I hope this helped!