This picture is absolutely beautiful! You really captured Fluttershy's grace and gentleness with the soft colors that you used. It has a nice childish feel to it as well, kind of like a crayon drawing.
As for things you could improve on, I think her ear is a little big for her head. It's not too big, but it could be smaller. Also, her back legs seem rather thin, but I would be careful if you were to try fattening them up.
Occasionally, the lighting and shadows in this picture are confusing to me, as there doesn't seem to be any definte light sources.
Overall, I believe that this is a great work of art, and it truly shows the essence of winter and Christmas.