miku~ >u< i used to draw her and rin/len all the time X'D i used to listen to a lot of vocaloid lol
for this pic i'd say her arms are quite long in comparison to her legs, the tie probably shouldnt be so pointy (the long part comes out of the top (not like a diamond on top of a diamond)) her eyes are green (not gray), and even if its just style, i think there should be more variety in line widths (the black outline is quite prominent in areas with more detail (all around the hair/ headphones))
but other than that its cute razz i prefer her long hair, but short looks good too, and i see you changed her hair elastic thingies XP
and one more thing: once you've finished drawing, consider resizing/ cropping your image. currently, miku's floating around the top half of the pic with a lot of white space on the sides (not good for the eyes)
but gl, and gj so far 'u'