Honestly, I wanted to make her very similar to Luna, so that she would cause a feeling of guilt and protection in Celestia, and that was one of the reasons she trusted Twilight so much, she saw Luna in Twilight and just wanted to make up for her mistakes.

Twilight has genes from the bat ponies, which was a species that emerged during the transformation of Nightmare moon, creating the unicorns, earthlings and bat pegasus, the Bat-pony. Today, the species is almost extinct, being maintained by the bat pegasus.

This breed doesn't come from the same species as the vampire ponies, it's just a mutated variant of the ponies.

Twilight's father is descended from a bat-unicorn, so she has genes that connect her to Luna

Her mission is friendship, but I think her title would be Princess of Harmony, because that's what friendships are all about. So I made her crown like the roots of the harmony tree.

The mohawk came from Athena's helmet.

The distorted background is an optical illusion that the magic in her hair causes, like a galaxy or black hole moving/distorting, it's just something visual.