I've reworked one of my newer pieces called Gliese 581 c (like the discovered "super-earth")
and as `priteeboy
suggested a new more moonlike texture for the planet in the foreground
The texture for the background planet is now a 16.000 pixel instead of a 8.000 pixel resolution texture wich was made from NASA images. The original render resolution was 6000x6000 for the big and 640x640 for the small one.
The planet texture for the smaller one is a texture from the moon phobos.
Here's the old one:
(HIT DOWNLOAD TO SEE IT IN FULL VIEW)