How do you create new terrain?

[Gil Galad]

I would like to be able to create some reletivly simple new terrain. Basically, just adaptations of what already exists, like, say, snow-covered hills, snow-covered pine trees, and plains hills. If you can let me know how these things can be made, please let me know. Thanks

- Gil Galad

 

[D. Boon's Ghost]

You may want to check out Snoopy's graphics mod somewhere around here. It has all of the things you listed, and then some. He did a very nice job with it.