If you want a decent freeware renderer you can download Bryce 5.5  It has terrains, trees and skys which you can tweak endlessly for your backgrounds and it is very easy to import a mesh and texture it within the program. Bryce is also very forgiving about importing less than perfect meshes; most ngons don't faze it. I use the free Wings3D for most of my general modeling needs. You might want to check out the new freeware Sculptris as well.