Here is an artist doing great renders with Terragen 2. While I have the older version of Terragen, his works remind me of why I would like to have the Terragen 2 program because you can do some great things with it!
This artist has a great tutorial about how to make castle-like terrains to add to one's Terragen program!
They have some great Terragen-related renders in their gallery!
I'm currently following their tutorial now!