Since we are nearly at the end of the competition I thought I would add a link here to a couple of excellent tutorials (not mine) about using Terragens Render Elements in Photoshop and Nuke.
Photoshop Tutorial
https://www.youtube.com/watch?v=LNv9iEdv4k4
Nuke Tutorial
https://www.youtube.com/watch?v=ihY_kp2rzxg&t=293s
It is a bit of a faf in Photoshop but worth the effort.