Atomic Gamer had an interview with Bruce Nesmith from Bethesda about their upcoming Shivering Isles addon for The Elder Scrolls IV: Oblivion.
Here's a snippet:
Jeff: The Shivering Isles are the domain of Daedric prince Sheogorath. What's the overall feel of the Isles like?
Bruce: We wanted a completely fresh look to everything. So we created all newart for the Shivering Isles. The ground, the trees, the rocks, even the sky isnew. All the creatures, clothing, buildings, even the water is new. When you first step into the Shivering Isles, it's quite breathtaking.
The Shivering Isles is divided into two regions, Mania and Dementia. The land is a reflection of Sheogorath and embodies his madness. Mania is a place of bright colors and wild growth. It has an Alice in Wonderland feel to it. Dementia is the darker side of madness. It's dark and brooding and filled with dead trees and rotting vegetation.