"The sky above the port was the color of television, tuned to a dead channel."
-the first line of William Gibson's "Neuromancer"
If that's not cyberpunk, I guess I don't know what is. In short, I think the colors are fine :y:
You definitely could add a character somewhere...I'd suggest one lying on the tree branch, with maybe one leg dangling over, you know? Of course, be careful not to disrupt the whole flowing feel you've go going so far. As for what that character should be, that's beyond my creative reign ;).
My only real critique at the moment is that the rock feels much too alike to the tree...which is expected with such a palette...maybe make it darker or something?
But I like the contrast of the harsh, angled lines of the tree branches versus the curvy, free lines of the sky and trunk of tree...not sure if it was intentional or not, but I like it :P.
Good luck!