Sketch - Planetscape
Click the images below to see a high-resolution version.
This sketch was done using only three circle designs from my explorations. Circle #1 is used for the stars, #7 for the planet itself, and a slightly modified version of #4 for the aura around the planet.
Here are some of the ones I generated along the way to the final one but rejected. I like to put these here so you can see that this is just an exploratary process. Although I ended up going with a simple near-monochrome palette, as you can see, I did try a whole bunch of colors as well.