Home-made asteroids

To make these:
Take a polystyrene ball.
Smack it with heavy objects, poke it with screwdrivers and pencils, cut it with craft knife, show no mercy.
Spray with a solvent based spray paint - I used Citadel Chaos Black spray.
The spray will cause the styrene to collapse, creating interesting shapes.
Paint with acrylic - start with black, add in white until it looks the way you want.