Yeah, that's a little silly in terms of coloring. Saving out several channels for different elements will allow final assembly in Photoshop. Because we're going to do things in a perspective mode, everything will be screenshots of Wilbur's 3D preview window, which is a little lower resolution than is ideal. I really ought to get a higher-resolution monitor one of these years or fix Wilbur to generate a larger image directly.
A bump map because it's often useful to bring drama from low to high.
sm_bump.png
A texture-shaded image because it gives a little interest to the high-frequency parts of the terrain (the edges).
sm_ts.png
A base color image is important to avoid a general black-and-white map. This is from the Wilbur V2 shader, adjusted to look like a forest / desert kind of terrain.
sm_color.png
Most folks are familiar with a simple shaded image, so we'll put one of those onto the stack as well.
sm_light.png
Wilbur supports a depth image, which can be used to get heavier strokes on depth discontinuities. After a little processing the raw depth image looks like this:
sm_depth.png
Might as well do contours and rivers as additional interest.
sm_river.png sm_contours.png
That's the parts. Most of the grayscale things will be multiplied together as the high-frequency detail on the image, which will be modulated with the background color to get the overall image.