I updated to the new version you released about a week ago, and none of the planet backgrounds work anymore, it's just using the vanilla textures. I opened the zip and renamed data-final-fixes.lua to data-updates.lua and this fixed the problem. I think the issue is that by putting your code in data-final-fixes, you're setting the values after Visible Planets in Space has already created the SpritePrototypes for the planet backgrounds.

I did notice your description mentions selecting the textures in the mod settings, which I was very confused by because I couldn't find any such setting. It took me a while but I figured out that is a separate mod called "Visible Planets in Space Settings", which isn't required and just allows you to mix and match different planet texture mods. That mod has its own code that explicitly references the textures from all the different mods, which I suspect is hiding this bug in your testing environment.