Does anyone know what program can be used to create space skyboxes, such that there is space in all directions without terrain? I've used Terragen up until now to create skyboxes to test with, but of course they contain terrain, and even with the terrain turned off, you only get a partial skybox. I hope to eventually create more interesting skyboxes than just stars, with color gases and nebulas, like in Homeworld or Eve Online. They make the space not feel so empty. Has anyone created images like this? Any pointers on where to start?

Well, I don't know of a program that can do this off the top of my head, but I did post a short tutorial on how to make environment maps from spherical maps. (ie: In my example I used a sphere with a seamless procedural texture applied to it to simulate a nebula.) While I talk specifically about Lightwave, this technique should be applicable to all 3D rendering programs.

Very interesting! That definitely gives me something to start with, I'll have to try it out. Thanks!