Adding more detail to planets like craters or mountains when pressing "c" to land camera.
When landing camera on New Horizons, make it as if you were in the spacecraft, and use WASD to move around and add thrusters to it.
Make the Mirror Tetrahedron reflect the sunlight and heat.
instead of launching materials as particles, why not launch a comet or asteroid with the materials on it.
If one of these ideas of if anyone else's are in a future update, I will play Universe Sandbox Everyday!