Generating random planet classes from real textures

The problem with using real textures is of course that they quickly become recognizable and repeating.

Quite a few variations inside planet classes can be achieved by randomly combining layers of of real object textures. Currently I use 2 to 3 layers (surface, air, clouds), with various types of transparency. The combination of textures and their transparency degree is modified randomly.

Apart from technique the results depend of the textures used, so what has to be done is finding the best ones available.

Since the difference are currently only visual, the classification is done entirely according to appearance:

no atmosphere: surface is completely visible like on most moons and planetoids
thin atmosphere:  occasional visible clouds with almost complete transparency like on Mars
normal atmosphere:  mixture of clouds and mostly transparent athosphere like on Earth
dense atmosphere:  dense clouds of no or very little transparency like on Venus or Titan
very dense atmosphere: athmospheric processes found on planet giants

(Click on the pictures for the full resolution images)

Dense Athmosphere examples:

Very dense atmosphere examples: