YAY for photoshop tutorials!
went through the whole planet making phase aswell when i started out, then i got bored...
heres a piece a friend of mine worked on, once he had been through the tutorials on it...
pretty much the same idea that u used, just more in depth
http://i37.photobucket.com/albums/e8...y-587x1024.jpg
made using photoshop and some other shit called terragen or something, cant remember
the main thing with yours, is use less blurry effects, work bigger, and work in more detail.
i find google images - rusted metal gives good results
i agree with miko for the shadowing but the glow around the planet itself (while is a nice touch : P) is a bit overthetop. while it is good you put a glow it is alot bigger then it should be, look at the photo miko placed in his last entry, the planet does have a glow but it is much more subtle... other then that your doing great keep it up ^.^