Latest development is procedural planet textures.
The textures map seamlessly on a 3D sphere and the procedure to create them comes from this.
Ported some of this code to c# and created some examples of how they look:
Earth-like planet with a lot of water
Mars-like planet with a lot of ICE?
And this is how they look mapped on a sphere and with atmospheric scattering!!
The nice thing is that they look much better than photographs of existing planets.
And off course they can be generated in all different sizes and colours.