Realistic Planets

[julvr]

I am thinking of doing a video short, and I want to make a very detailed planet. The planet would include clouds, atmosphere, mountains, greenary and a few cities, and has to look good on a 1080p display (where one shot will show half the planet on two thirds of the screen (so in reality, it has to look good at 1400 x 1400 pixels).

I'm wondering if anyone has any good ideas about how to do the clouds, atmosphere, and generate a detailed terrain map.

Thanks,

John