if I compare your screenshots of the planet, your last screenshot looks really nice!
Although I know, that shaders are for the end of a game-development-state for "buffing" I wanted to write down the things that came to my sense as I saw your screenshot:

If the camera can be very near to the planets in your game, maybe you could add a bump-mapping/normalmapping to see some unevenness? Your planet reminds me to a athmosphere-shader in the wiki, just in the case, you didn't noticed it, here the link , maybe its helpful

As Error014 mentioned, I am happy about your stuff, too, it looks nice so far and I am looking forward to see some game-mechanic in action!!