in reply to PM merchandise/icon design quest
Posters would be great.
Monks meditating in front of terminals
Picture/Phrase Combos
A large chunk of code colored in such a way that it creates a larger image
Parody posters (such as the WWII one mentioned above)
The Coder's Commandments, and other such important thing
Perl Poetry
An approxant map of the internet at one point in time
A diagram of program code
etc.
The artistic posibilities are endless, and posters can greatly add to the atmosphere of a room, cubical, or public place.