While a lot of this stuff is “Well, Duh,” there’s still more than enough interesting commentary in Lukas Mathis’ fascinating examination of realism in UIs.
Most UI elements are symbols of objects but many are significant objects in themselves, symbolic representations of functionality or whimsy. For example:
Coda’s leaf isn’t a representation of the idea of a leaf; it’s a very specific leaf, the Coda leaf. Acorn’s acorn isn’t just any acorn, it’s the Acorn. Adding details moves these images from a generic concept towards a specific entity, and in the case of an application icon, this is exactly what you want.
The goal in UI design is to decide what needs to be stripped down and what needs to remain realistic. Great Friday reading.