Again, taken from the SO suggested list, but this does seem like a good question.
Anyone have any ideas?
I think the feel of the design is more important than specifics. I'd like an air of weightiness, seriousness, sobriety, intellect, the Enlightenment tradition.
Particular design elements might include some foundational equations, a stylised chart of intersecting supply & demand curves.
Oh, and maybe a picture of David Ricardo stood at the top of Everest in a t-shirt and tennis shoes (hat-tip David Friedman)
I would love the design to incorporate the Mainline Economists Mural at Universidad Francisco Marroquín.
A illustrated bookshelf of the most important books in economic thought could work: Wikipedia has a decent list but I suggest confining ourselves to deceased authors.