Finally finished this! I did take inspiration from the Diamond murals from the show and @ for the wings. They are gorgeous and I highly recommend watching this artist!
 
The Tree of Harmony is White Diamond. An all seeing goddess why I is stuck in her head. She believes she’s doing the right thing by instilling these rules, and doesn’t really mean to be such a horrible person.
 
Yellow Diamond is Sunset Shimmer. Mostly based on the first Equestria Girls movie, where she’s a huge bitch. Sunset is a hard ass and wants everyone under her control at all times.
 
Blue is Luna, if course. Luna is a sweet, kinder alicorn who actually somewhat cares about her people but is heartbroken after losing Tia. She wants to be a good pony but isn’t quite sure how.
 
Tia, of course, is Pink. They are a brat but they do genuinely want to bring happiness to others, for others to be free to do what they are and and love.