To start here I must say I absolutely adore your art style! The lighting is so beautiful along with the reflections in the eyes. Another major thing I love in this is that you didn't use the dull common colour black. You have some greys, but it makes the piece bright, happy and vibrant. The way you shaded also looks very good with the shading of how the body is shaped different to how lighting is effecting rarity the pony which makes the her stand out from the other objects in the picture.

The only critique I can give is maybe to look at the anatomy of horses, ponies or my little pony characters again as her neck seems to be a little long as it is longer than her legs.

Back to another good point I think you got all of rarity's colour pallet perfect. You drew the mane without one mistake as every single strand of hair is in the correct place.

Overall I think you did very well with this piece.