This is another play on words to capture the customer's attention.
Everyone loves a play on words - even cats.
In addition to an image or depiction of an activity (guitar playing, racing, etc), these shirts often use a pun or play on words and a touch of humor to add interest.
You may also want to look at how you might be able to create a play on words that have to do with your school team name.
For example, Pringles used a play on words of Devo's Whip It to promote their potato chips.