Here's a stab at alicorn!Twilight, maybe some years from now. I tried to come up with a nice blend of regal princess-ness and Twilight's characteristics. Like giving her a swoopy mane that still has that squared-off shape to it.
It still surprises me that the main color in Twilight's mane and tail is more blue than purple. I have to think of it as "indigo" to get it right.
Prismacolor pencils on Strathmore sketch paper
Edit: Please see this lovely vectored version
! She did a great job.