In some ways, the sketch has a charm all its own that could serve as a piece of finished art. I think illustrators often like our sketches better than the finished art for their looseness and spontaneity.
Illustrations copyright J. Pittman, 2008
You can see the sketch, of course, is pencil, while the finished art is pen and ink. The color, in both cases, was done digitally in Corel Painter. The finished art's color was made a little more intense and using blue reflected light for more contrast. The background was changed to be more of a vignette. Either drawing would have probably worked, but the whole series was done with pen and ink with crosshatching to complement the color washes.