If you're looking for realism, you'd probably want to photo-source your textures and not make the logs perfectly straight. Give them some irregularity. Also, at the ends, you'd want to have the naked wood show, with the rings on the caps. Put some nicks and cut patterns, a knot in the wood now and then, maybe some had branches that were cut off, etc etc. Realism comes with the details.
As for the sky, again, photo sources couldn't hurt. You'd also want the stars to have a high diffuse so they show up. Maybe some incandesence(sp). That kind of thing. Map it onto a big half-sphere around your scene and you should be set.