There are two new world types in the current versions of this mod. Both have a similar theme, but a totally different way to generate the terrain.

-Old Ice Mountains (IceMountains): The old version of the terrain generation. It is not too fancy. But for the sake of not throwing it out the window, i kept it in the mod. This version does not simulate erosion. It simply consists of 3 perlin noise functions which are overlapping. Known issue: moutains can exceed a height of 256 blocks, which will result in them being chopped off.

-Ice Mountains (IceMountainsE): The new version of the terrain generation. If you start a new world with a new seed, expect to wait around 3 minutes. It will generate 4 heightmaps which cover an area of 4096x4096 blocks. Within that area, the terrain will be generated quite quickly. It is not a bug. In order to simulate erosion properly, a large area needs to be taken into account at once. So chunk per chunk generation is simply not possible like in the old version. However, that should not discourage you from playing on that world type. There are not many biomes yet. So far only forests, swamps, oceans and of course the ice mountains.

In some screenshots/renders i used the ChromaHills 128x128 resource pack. It can be found there:
https://www.chromahills.com

And just for fun: Some massive Chunky renders (IceMountainsE v0.2)!
http://gigapan.com/gigapans/219271
http://gigapan.com/gigapans/219277