Awesome renders, but as they are right now, that is all they are, awesome renders.
A skybox looks a bit different and there's a special procedure used to create the 6 images used as an actual skybox.
Now if you are willing to create that kind of sxyboxes, well that would be fantastic.
The basic principle is simple, create an environment, and then take "photos" of it via terragen built in camera.
You need 6 photos, top, bottom, left, right, back and front.
So it's just a matter of angles, or on other words rotating the camera by 90 degrees until you all sides have been covered.
Maybe this will help.https://www.terathon.com/wiki/index.php ... g_Terragen