Just looking at the thumbnail of this picture, I was mesmerized. The different shades of blue really complement each other without overpowering one another; you made a great decision in using mostly blue in this picture.
I really like the details in the wings; the feathers are nicely done, and the texture looks a lot like a bird's feathers (particularly on the back). I like how the individual feathers are a lighter shade of blue.. they really stand out..
The background alone is fantastic, as well. The clouds look professionally done, though I think the sky looks a bit too dark.
If I were to nitpick, I would say that the ice beam looks a bit odd (I sort of imagined the move as a stream of ice. Here, it looks more like a tangle of ribbons). The tail could have been given a little more detail, I think. But other than that, this is an excellent piece. A simple theme, but effective.
By the way, I only gave originality a 4 because a picture of a pokemon using Ice Beam isn't exactly new. To keep with the theme of blueness and ice, I probably would have drawn Articuno using Sheer Cold or Blizzard. But, don't let that bother you; it's hard to draw something no one else has done.