Sad we only have Overworld Skybox and End portal effect.
Nice, but could be a ton better, I'd love if we also had the following available:

• Nether Skybox
• End Skybox
• Perpetual Overworld Day Time Skybox
• Perpetual Overworld Night Time Skybox

After testing the mod, i can say i like it, but i really think we should have more options.
A nice little naming convention would be "Skybox: "
Name examples:

• Skybox: Overworld, Day cycle
• Skybox: Nether
• Skybox: Overworld, Always Night
• Skybox: End Portal Effect
• etc...

Well, just my ideas and requests.