Lots of pencil sharpening going on over at Hooptyrides, Inc.
If you can convince the pencils to cooperate, each can represent a four-bit pixel. Length, shaft color, sharpness and lead color. If you really want to get secret message-y, I suspect you could communicate tons of data in an arcane pencil language. Add diameter, round or faceted, eraser condition and a dot/dash morse code of bite marks.