Currently there are 5 biomes: MOUNTAINS, SNOW, DESERT, FOREST, PLAINS. There's an ancient GitHub issue requesting different forest biomes and I'm currently porting a worldgen that supports many biomes:
OCEAN,
LAKE,
BEACH,
SNOW,
TUNDRA,
BARE,
SCORCHED
TAIGA,
SHRUBLAND,
TEMPERATE_DESERT...