Thanks for the comment, zach! Even though the pic from your link said, "Strap on some plums.", I did manage to find THE YC T-Shirt pic from it so it's all good:

http://www.shoutfit.com/items/51371/in/closet/ickmonst/in/trend/38

Also, there's a link above it that takes you to YC's Shoutfit category, "Y Combinator Gear". Perhaps a new design is in order?