I've been playing around with the parameters. Here are some of my results:

More colorful world pattern:
max extra: 2

Sphere world:
Building block: Data/Objects/primitives/smooth_sphere.xml
Local Block scale: 1.3
World size: 10
Block scale 2-3

Mountain cliff:
Buldingblock: Data/Objects/Rocks/rock1a.xml
Local Block scale: 0.5
Block scale 2-3

For Rock color:
Max color: 2.5
Min color: 2.3
Only thing is that they generate very late.

MacBeth:
Buildinhblock: Data/Objects/macbeth_cube.xml