I think the shakiness is mostly an issue with your curved lines, like on the top of the hood. I can't really explain it too well, but here's a picture that shows the difference between a jagged and smooth curve:



The lines look better! For future reference just think of how the light source would affect your outline. It shouldn't blend into your main colors, but shouldn't be as harsh as regular line art as well.

And I really like that striped sweater. I think the shape of the avatar's left arm is a little wobbly, though.