Custom Biomes adds biomes to the rest of the celestial bodies in KSP. It also allows for the replacement of any biomes already in the game. It runs automatically in the background at startup, and doesn't require any user intervention. The biomes are fully compatible with KSP's science system, and display correctly for mods like SCANsat as well.
To install, simply extract the CustomBiomes folder into your GameData directory.
Custom Biomes supports user customizable biomes for any celestial body, so it should be compatible with mods that add new planets. What it does not have yet is an expanded ScienceDefs file for custom results for the new biomes. I have made a set of terrain maps (from SCANsat) available in case anyone wants to make their own biomes.