(http://assets.cgsociety.org/nvart/254255_1212967013/1024bound)The 3D parts of this image -- the planet and moon -- were created with Maya 7.0 and rendered with mental ray. Textures were generated using Photoshop CS and Darktree Textures 2.51. The nebula and starfield were painted in Photoshop CS, and final compositing and 2D work was done in the same program.
At the end, I stated playing around with the colour palette. I kind of liked the way this green version looked; it has a very different feel than the original magenta version.