I like the idea of putting '21' in a shape like you did in #20.
Instead of the current round shape can you do a drawing that looks like an artichoke lamp or Poulsen PH5 lamp and put the number '21' inside?
Images of both lamps:
http://cargobikehandyman.blogspot.com/2011/04/louis-poulsen-ph5.htmlThanks!