Last summer I entered the Gamblin paint company Torrit Grey competition with this. You have to paint a picture just with black, white, and Torrit Grey, which they make every year from all the pigment caught in their filters. That idea charmed me; and the paint is really nice. I didn't win, but they sent me two more tubes of paint for participating and the picture's included in the gallery of entries.
This was the first place winner:
And I particularly liked this Honorable Mention: