how to create custom environments?

I think the title speaks for itself... How do I create a custom environment? I need to make an "end of the world" effect for my "Apocalypse" coaster. Thanks in advence, you coaster geniuses out there. [:)]

[img]D:/charlie/nolimits%20coasters%20v1/cjdsignature.jpg[/img]

The program to make it:
http://www.coastersims.com/tia/environmental/index.htm

With this program you can add images to be a texture for the station for example. Just post your questions here if you have any.

Greetz