First, for the vision and originality I gave 3.5 stars. I feel like this isn't extremely original, but it makes up for that in epicness and impact...
Technique: I feel like this is one of your best yet and I say that because it clearly shows you are starting to develop a personal style. You are letting go of outlines for the sake of realism and it's turning out rather well.
Impact: the impact of this is rather striking. I feel like that is the strength of this piece. While it has a maybe boring portrait style centered composition it does manage to grab your attention. And that is mainly to do with the face that she is looking directly at the viewer. The colourwork and shading is also very striking.
"In place of a princess, you would have a QUEEN! NOT DARK BUT BEAUTIFUL AND TERRIBLE AS THE DAWN!! TREACHEROUS AS THE SEA!! STRONGER THAN THE FOUNDATIONS OF EQUESTRIA!! ALL SHALL LOVE ME AND DESPAIR!!"
Total foreshadowing right here. Wouldn't be surprised to see Twilight dip into dark magic in the Season 4 premier. Maybe as an added boost to handling all the stress that comes with being a princess perhaps?