Mostly just QoL updates and new things to do in existing biomes and make of existing materials,although some new have been added to existing biomes..
Plains, mountains, and swamp have seen some love that way.
Remember for example how troll was the last and best light armor available back then, since no light armors existed from biomes after blackforest?
That's one example of geartypes where new stuff got added.
(Something I appreciate since I found the light armor line being rather lacking.)

New biome mistlands is in testing together with a bunch of changes that may or may not reach live.

Edit addition: They've basically been fleshing out the biomes that didn't feel complete.