So I've been working on a system to emulate the image of earth from the 1972 Apollo-17 mission, using procedural methods. It comes reasonably close, and still works pretty well in game:
SectType.txt entry:
Physical Type := Planet
Picture Num := 302
Description := Inhabited by a pre-warp civilization of ape-like creatures.
Planet Size := Medium
Planet Physical Type := Rock
Planet Atmosphere := Oxygen