The design can include PhotoQuotes logo or the photoquotes url.
It can be be one or two side t-shirt design.
I think it would be cool to use some of the quotes from the site as part of the design but it is not required.
Think about "what a college student would want to wear".
I really like the http://www.threadless.com/ t-shirts.
Some cool quotes:
"There are always two people in every picture: the photographer and the viewer."- Ansel Adams
"Your first 10,000 photographs are your worst."
- Henri Cartier-Bresson
"The quickest way to make money at photography is to sell your camera."- Anonymous
"If I could tell the story in words, I wouldn't need to lug around a camera." - Lewis Wickes Hine
"While photographs may not lie, liars may photograph." - Lewis Wickes Hine