Somehow I am in SciFi mood...
(http://reusch-axel.de/gallery/thumb_big_intergalactic1280.jpg) (http://reusch-axel.de/gallery/intergalactic1280.jpg)
C&C welcome.
The atmosphere of the close planet seems a little skinny, or maybe it is the mountains that are too tall. Either way, it seems strange to me to have mountains reaching the limits of the upper atmosphere.
I agree with above... You have some good details here, and the render is good quality too. But IMO, I think the planets appear to close together. Also the background is not working well at all. But I think it is a very good start. Just start tweeking away.