Concerning Yliakum's sky, the explanation
The Wandering Djinn gave you accurately described the world. Have you taken a look at the
setting part of the website? We live in a hollowed out stalactite, with several levels:
"A huge single crystal known as the Azure Sun connects the stalactite to the surface of this planet, and allows light from the star that this planet orbits, to enter the hollowed out stalactite." So, nighttime occurs as the outside planet spins around its sun. Light from the outside filters through the crystal; when there is no light outside, there is no light in Yliakum. There is no rising/setting sun, and thus the sky is a lot less dynamic than it is here on earth. I do agree that improvements still need to be made to the skybox texture.
When referring to a current terrain designer, are you speaking of the texture part, or the actual 3D maps?