Well, obviously more biomes, but that's already planned. Namely the ashlands and mistlands.

Right off the top of my head...
- A way to get more inventory slots, like a backpack or something, would be nice.
- Wearable lanterns as a craftable alternative to the glowing headpiece thing. Make it consume resin or coal at regular intervals to balance it out. Maybe wearable as the belt-slot instead of the helmet.
- Quality of life thing, but rework the stonecutter. Like, a temporary buff when you interact with it that allows you to craft walls wherever. Would definitely be better than having to constantly move the damn stonecutter around in order to make any decent sized structure..