PypeBros, they're not pasted, everything has been done manualy. At first I was drawing them as boxes and then decided to change shapes and make more variable volume. Thanks for pointing out, I've applied changes for these parts. Other parts may also require changes, but I'm afraid to make it too detailed for a background. They are already too detailed in my opinion and I don't know how to make a gracefull downgrade. I also need to study rocks more, you are right. Thanks a lot for advices!
jinza, mitDebo, sorry guys, I've spent on this piece four days. I'm not ready to spend another four making a tutorial. -_- Really sorry.