What are these strange creatures?... they are most definitely not ponies.
I know the whole "Day and Night" shtick has been done innumerable times between our two royal fair maidens (heh), but to see one that includes Twilight in the mix is a rare sight for me. It's even more rare that I see one with humanized artwork so I figured I'd have a crack at it.
I say it's a fascinating thought, imagining how these ponies would look and act had they instead been humans. Though I can't say I regularly have such thoughts... so yes, it is fascinating.
This is one of my favorite pictures from the fandom, and is currently the wallpaper on my phone. That being said, your crescent moon is backwards; the light part is always towards the sun.
I always thought of Celestia being a bit darker myself. Though me I would make twilight pale mostly for the reason that she was a bit of a recluse (it looked like it to me at the beginning of the show) just cause the fur is white doesn't mean that it has to be white underneath. And your logic about Luna makes sense for her skin as well :3
I've often seen humanised versions of Luna and Twilight as black. but the is the first black Celestia I have seen. Surprisingly I like it more than the other two.