Yeah they are a Reflective Shader applied on the fake stones. For the next attempt I will try reducing the cloud density too see what I get, altough it was my intention to have these dark and heavy clouds...
And maybe the stones on foreground are too regular-distributed, I'll also try to change that...
I'm afraid that a ship won't fit the scale to it, as the camera is really near the ground and the view is narrow, but it's a good idea to have some ship debris in the middle of it, the only thing is that I don't know to model that...

And maybe its rather difficult to find for free download...
Anyways, thanks everyone for the response!