[Suggestion] Ice caves
The way Ice caves are laid is pretty great. Larger, deeper, and you have to build some structures to exploit them.
Suggestion is to have a network of caves, tunnels, ridges, abyssals you'd have to build a bridge to cross, a labyrinth where you could get lost and also have a more claustrophobic experience. Caves could also have limited vision, or connect with breakable stone or ice walls.
Also this opens a potential for underground critters.
ice caverns and networks as well as rock cave networks would add another interesting level of intrigue to the game for sure along with cave dwelling creatures or wildlife.
This would be another use for rope being able to climb up and down rock and ice cavern walls or caves that can only be reached by rope dropping down or allowing pick and shovel to be used to get in and out on a incline that is walkable or jumpable.
Another idea is add rope bridge building and ice climbing with ice pick and rope.