Applying biomes to a Wilbur-enhanced map...?

[arsheesh]

Well, I don't know that this is really an "easy" solution, but rather than using the default Wilbur shader you could create your own height color gradient maps. What I do is start with a Gradient Map to designate Temperate biomes, then create one to designate desert/arid biomes, and finally one to designate tundra and arctic biomes. Then I place opaque layer masks over the Arctic and Desert layers, paint in the areas where I want them to show up and apply a Gaussian blur effect to help better show the gradual shift from one biome to the next. Below I've posted cropped copies of some of the gradient maps that I'm using in my current map, as well as what they look like once combined the way I described.

Cheers,
-Arsheesh