In our first few demos, the background of the scene was always plainly colored—black or blue. Not very realistic, but acceptable if the indoor player only catches a glimpse of something blue through the blinds anyway. Now that the game scene is no longer set underground or indoors, you face the question of how to design a natural background.
The horizon is so far away—it might as well be a flat backdrop on a theatre stage. In fact, the sky in video games is just that: a flat, pre-rendered image. You can find free sky images online, but typically, you design custom skies that fit your game's atmosphere.
Note
Don't create a large 3D model filled with skyscrapers and mountains as background. A huge model may look pretty; rendering it will, however, slow down your game at runtime. It's also a waste of your artist's time, especially if the player will never see these models close up.
Scenery generators (such as Bryce or Terragen) are graphic tools that specialize in...