a good start! i'd take a look at the project file but I'm no celestial genius, Will would be the one you'd need for this.
only two real crits:
1) Increase the size of the clouds, to do this open the cloud layer's density fractal and increase the sizes in the first tab, try by a factor of 10 or 20. Also, check out the procedural clouds from space thread in general discussion, there you'll find a clip file for some quite exquisite from-space clouds.
2) the far planet needs it's atmosphere samples increased. You'll have to go to the atmosphere shader in the second planet though, not the atmosphere tab. to do this, select the new planet in the objects tab and open it's properties and find where it says what the atmosphere shader is, click on it and click "go to ..." and edit the properties there as if it were a normal atmosphere shader.