http://www.planetside.co.uk/
I doubt Terragen was used for T2. (It's not even a complete work yet) but it is indeed pretty cool. I discovered this little gem last year. It generates a landscape according to the user's modifications of climat, altitude, snow pattern, etc. It makes some very cool wallpaper even if you have no clue wtf you're doing. I recommend it to anybody with a good PC and a wanting to make nice wallpapers.
A few examples :
http://www.planetside.co.uk/terragen.../antarctic.jpg
http://www.planetside.co.uk/terragen...s/paradise.jpg
http://www.planetside.co.uk/terragen...s/snowpeak.jpg