I found these interesting philosophy t-shirts / posters / etc. at Cafe Press.com. There are over 42,000 designs and almost 1/2 million products that you can buy these designs on.
There are some fun t-shirts there like "Plato's Cave Alumni" or "Philosoraptor" or a bumper sticker that said "Major in Philosophy: It's By Far the Most Interesting Path to Poverty".
Others were "Don't argue with me, I have a philosophy degree" and "I doubt, therefore, I might be..." "Team Schopenhauer / Nietchze / insert your favorite philosopher", and one of my favorites: "Sure, it works in practice, but does it work in theory?"
And no, I'm not a shill for this company.