I like the varied strokes you used to create this particular picture. One somewhat odd thing is where the wings are coming from-while even, they look like the bases terminate at her cutie mark, which is entirely too far back. The wings themselves are nice in terms of general shape, but look rather messy when it comes to actual feathers.
Her mane and tail-I'm not sure if you were going for 'Luna just returned from the moon', in which case they should be shorter, or 'Luna growing back into about where she should be now', in which case they should be ethereal, flowing, and full of stars. Her horn should also be a bit longer.
I really like the feel of the picture-like she was happily and casually fluttering along when this picture was caught, making her look happy and approachable. This sets you apart from most that draw Luna, as so many draw her as a dark and mysterious, unapproachable being.