Blue Planet By eXecutiOner
Out of the bowels of my laptop comes this, the first sky box I have ever made. It is a very good sky box to use in a level set in a spaceship. There is a blue planet that is in a orbit around a star in back of it.

The UNIT 4 Quake 2 Skybox By IdSoftware
I like this sky box a lot. It is very nicely made and is perfect for a level in which you want an orange sky or want some sort of alien like setting.

MTN By eXecutiOner
Yes, I did make this beautiful sky box. Well kind of, this is the default sky box that comes up when you open up this really cool Photoshop plugin called SkyPaint GE. This is perfect for a level that takes place in the early morning in the desert.