See this biome site that inspired my biome system
http://www.blueplanetbiomes.org/world_biomes.htm if anything taiga is the transition from tundra to temperate biomes.
Priority now is testing and settling the primary surface shape / elevation map, then i want to add many more biomes (although i don't own Minecraft i love watching the multiplayer videos, and have been inspired by Biomes A Plenty. I intend to use another large scale noise to slowly switch through several biomes in each of the 9 temp/humidity sectors, so you can have multiple temperate forests ... i could also move to a 16 sector system.
Mid water could be done easily by just making all water at y = 2 mid coloured, might try it since it's so easy. Renewable river water spreads it's sources and makes a mess of the inclined shape of the rivers.
Those clouds are at every 80 vertical nodes and extend throughout the atmosphere and floatlands.
Good idea to make snowdrift compatible ...