Im guessing in your human-canon Earth Ponies are Humans, Pegasi are Angels (as a species, not a spirit), and Unicorns are Elves. Alicorns seem to be the combination of all 3 to be some sort of demi-gods.
This reminds me of the story my friend Sour Grapes and I are writing on FIMfiction. (The Sour Grapes Chronicles) Specifically a character based off of the Bat-winged ponies that flew Luna in for Nightmare Night.
Is there any chance we'll see what those Night Ponies look like humanised?
I love the art and the design... ...but I must say, I'm not fond of the ears. It's one of the illogical WTF moments I have with art. When artists say their going to humanize them then add a whole bunch of pointless extras to them (like a horn, color, snouts... even sometimes the wings get to me)... it just makes them... ...not human