Thanks for all the replies! Here's the second version of the example, with stars and an unimplemented dawn sky (if you implement it, be sure to post here for all us others to see) - updated the building sprites up a notch (again, don't use in other projects please ). Stars have a glow effect. Building glow removed due to it almost halving FPS on older computers!
Edit: Argh, Glow sure is FPS heavy! Here's a hotfix which makes the stars use additive blend instead: