Would not landuse = farm be appropriate for terrace farming and maybe we could add something like terrace = yes. Most of these land pockets usually have rice, wheat, maize or paddy. This type of terrace farming is also done in mountain region of China.
Receding glaciers create a number of natural features which dont have obvious tags (outwash plains, former glacier beds), but prominent lateral moraines can be mapped with natural=moraine or geological=moraine.
For remote mappers any photographs of rural areas which can assist in interpreting aerial images are extremely helpful: villages, farmland for crops, roads, paths, forests. Just a couple of pictures can often really make the difference between guesswork and putting in place a baseline map.