Add the semblance of life to planets
Allow Voxel types to have a particle effect bound to them with biome restrictions.
e.g I create a volcanic biome allow my lava voxel to have a small steam particle generator attached and then LOD them for distance, Then a volcano in the distance would have the effect of giving off gasses and the effect can be greater or lesser depending on altitude.
Add Effect to Grass Voxels that is random where walking close to one generates insects being scared out of the grass. same for trees and Birds.
Add birds flying randomly in the sky and random animal noises.
They don't have to be interactive just ambient effects.