I really like this shinign effect on horse's hairs <33 and really lovely colors you choosed! One thing important you forgot it's that you hadn't add shadow under horse! And it looks like he is pasted on this background. Next thing is this horse is to big to all background and makes him giant-look.
The horse is really well drawn and the background is amazing, but they don't look good together. Looks like poorly done photo manipulation. You need to add a shadow under the horse, make some grass blades visible in front of his hooves and between hair in his tail where it lays on the ground, maybe a little dirt on his legs. And I would consider changing the light on him to be a little warmer, but I'm not so sure about this. Still, it's really well done.
That's really cool. I like the pose, the head leaning downward with the flowing black mane makes the pose feel quite moody. Lovely detail on the face too, the nose looks particularly realistic as do the wings. Awesome work!
Well done! I love the sparkly horse. One suggestion, though, would be to darken the shadow beneath the horse - right now it doesn't look connected to the ground. The background is great - I love the textures here!