This mod improves the following:

Stars will twinkle and be of slightly different colours

This mod renders a seed/server-dependent skybox that is 100% generated in runtime with cool shader-like nebulas.

The lightmap has been a little tweaked to my personal preference to be a little more vibrant and dark, but it's 100% sure that these changes will be optional in the final product.

The mod does not work with most shaderpacks, but it does work (and looks really nice) with Complementary Reimagined (and probably some others, but I haven't tested them).