It's not bad. Looking at your space art, you seem to be fond of the blue hue, I would start experimenting with more colours. The detail on the planets is nice, but you really need to work on your stars, as well as, maybe incorporating something more into them? Maybe a ship, satellite etc, or more interesting cloud formations. Just my thoughts.

Take a look at Erik and Seb's work :

http://kire1987.deviantart.com/
http://shue13.deviantart.com/

hope that helps!