TL;DR: Added terrain materials, a cave and tweaked the player controls.
Finally got comfortable with basic terrain material blending. Added rock and some subtle melted snow in some areas.
Made a cave in Blender and improved my manual UV unwrapping skills., though I try to avoid it when possible.
Found a nice minimalistic untextured cabin on Blendswap. I realized that the key to using premade assets is to texture them yourself so that they properly blend in with the surrounding environment.
Concerning player controls, it was originally setup so that you couldn’t turn mid-air. I thought that it would raise the stakes and make it more fun, but it mostly ended up being annoying. Now the player can turn in mid-air. Good gameplay or realism. Choose one.