So, someone compiled a list of Princesses that can be used. I imagine there are more in the canon universe and based on the story you write, it could be an even wider variety, but here's what we got so far:

Princesses so far
Celestia
Luna
Cadence
Twilight
Dream Big Mac
Skystar
Platinum
Amore
Black Snooty?
Flurry Heart
Erroria
Spike (At the summit)
Ember

If you all can think of more that I'm not aware of for reference, just comment them below.

6528747 It took me far longer than it should have to realize who The Abomination was.

Should we maybe post a list of the villains that are usable as well?

I completely forgot about Flurry! You guys are gonna go crazy when you read my groundbreaking story about the forbidden love between Discord and a baby.

6528844
Commit dead.

6528747
Does Ember not count? And what about honorary princesses like Diamond Tiara?

6528973
Holy shit, how has nobody thought of Ember yet? You sir or ma'am, are a genius.

6528983
I wasn't even going to use her, but I didn't see her on the list and I had to ask.

6528747
Wait, we can use Big Mac?

What?

6529948
Remember that dream episode from back in the day? He was a princess in the dream world.

6529953
Oh, I remember. That was a good episode. But I wouldn't have thought that would count.

btw, Black Snooty? Nightmare Moon?

6528973
Ember is genius. Mind you I'm not ditching my concept for it, but that's got alot of potential.

6528818

A villain list would be really useful

6542283
Especially since there's valid concern over "villain vs antagonist."

Say, Flim-Flam, as an example. Or Pinkie clones.

Also, presumably the story could be set further in the past, if working with the elder princesses?