This is really adorable!
I love how the horse is sticking it's tongue out like that! The tongue is adorably pink and stuck out in a 'realistic' manner.
The 'airplane' ears look perfect and match well with the tongue sticking out. The horse's eyes look hilarious and they seem to be watching the snowflakes, right? I personally have trouble drawing horses facing forwards, but you've done fabulous with the correct anatomy.
I also like the rest of the body, and I also love how it's slightly blurred, making the horse's head the center of focus. The green blanket is realistic and has well drawn buckles. It's sitting on the horse in a way that you can still see it's a horse under there!
The shading is fine, and fine for the way the amount of horse shown. I like the shading on the blanket most, because the contrast is really nice. Your shading definitely shows where light is coming from, and how much light there is.
The background is splendid! The basic color is a winter gradient, which really gives off a sense of cool air. The snow looks fine, and I like how some have a lower opacity to show near and far.
This piece is really creative and cartoony, it's awesome!
Wonderful creativity, and wonderful way of expressing it!