Heather's right about Drawing and Illustration. Depending on the subject, a piece may also fit in one of the genre categories. As far as the galleries go, you would put your work in Drawings and Studies. Don't forget there are galleries for subject, too. Since you can put your work in up to three appropriate galleries, it's good to explore all of your options.
associate director, EBSQ
I believe that everyone else my age is an adult whereas I am merely in disguise. - Margaret Atwood