I am working on user manual, but it still isn't ready, sorry for this.
As for .tgd-sources for pictures, I can't upload these as the most pictures (those that are the most impressive) aren't mine, they are created by very talented Terragen artists, namely Ulco and Martin. That canyon scene was created and rendered by Martin.
I can share my canyon, but it is quite mediocre, I am a poor artist.
I've attached .tgd scene and two renders (without and with thermal erosion).
I used powerfractal, fractal warp shader, strata shader, small powerfractal, one erosion layer and strata shader after it. As far as I know Martin used two erosion layers and also added powerfractal after erosion shaders for some additional details.
Daniil