Quote: "I thought of that too, but it still nags me that I cannot simply edit and rename skyboxes.
Is the .x file somehow tied to the name of the skybox folder and the picture names?"
The X file will have the texture file(s) listing inside. For example, using Cosmic's skybox from his Pirate Pack (Lost At Sea). If I want to change the .jpg to .png, I change the textures and then edit the X file and any reference pointing to *.jpg is changed to *.png.
As far as renaming, there are no issues that we have seen. We've taken one skybox called PTI (Pirate Treasure Island), renamed it to PT1, made a copy of it and called the copy PT2. That PT2 texture was then changed to a nighttime scene and we never had problems.
Unfortunately, if jpg support was dropped in v1.18+, then that will cause those using v1.18+ to have to alter some of the media they have to allow for the change. One of the reasons we elected to remain in the version we did- to have jpg support.

Twitter: @NFoxMedia