Character concepts for children's story

I have been working on the above characters for my Illustration for Publication class. I first designed the characters, based on descriptions given in a children's story manuscript, and then did drawings of what they would look like from various angles. The characters themselves are four girls, two older than the others, and they are supposed to be racially diverse (I don't want to give away too much, but that is the gist).

We had to do one drawing of each character fully rendered in the medium we would do full black and white (no color :-( illustrations in, if we were chosen to fully illustrate the manuscript. I would have done the illustrations in a digital medium, but given the story's sort of outdoorsy nature, I wanted to stick to a media that was more organic. Not that this can't be achieved digitally, maybe i just wanted the additional challenge of something non-digital. I dunno.

I decided to render the characters in graphite first, to get a feel for how i would render them in gray tones. Then I chose to do one character each in Payne's Gray watercolor. (The characters with the shadows underneath them have been rendered in watercolor, with some blacks added in Micron pen.) I used a surface that was new to me, Aquaboard, which is a clayboard meant for watercolors. I actually really liked it. I got relatively clean gradations, and was able to work with the brush in a way similar to my Prismacolor colored pencils.

Let me know what you think!