This is very nice! I really like it!^^ HOWEVER, Nighmare Moon's cutie mark isn't right, if you'll look at screenshots you'll see it goes farther down her leg than that. Even so, this is very good! Celestia's wings are gynormus (that's a good thing) and I love the way you did their slippers! Nightmare's collar is a bit too high, it should be somewhat lower and Celestia's. Their tails are perfect, but I'm not sure I like where their standing...is that a desert? It seems more appropriate that this be situated on a cloud, since they are Alicorns. One last thing, you should have made the green in Celestia's mane brighter. I can barely see it, but the other colors in her mane look ok.
Overall, This is a really good picture and you will be seeing this in my favorites! ^^ Nice job!
this actually looks really good!~ you have the anatomy down, although the poses are a bit stiff, it doesn't detract from the picture!
one of the main things about MLP fanart is that it's usually always in the show's style!! maybe trying to draw a pony in your own style would make it a little more interesting...? not to be rude safdsfdds u//w//u