Having longer ears would defiantly help make the horse beautiful.
If you hold your hand over the ears and imagine what type/size (of ear)the horse would look good with, then pull your hand away and you can tell it's too small. Am I explaining that okay?
As in I put my hand over the ears and imagined long delicate ears that are slightly forward (because the horse is looking at something with interest, so the ears would be also pricked forward....see the horse in my avatar)but then I pulled my hand away and could see how much shorter they were then what I "saw"....
Also the mane could have a little more "top" to it I think.
Otherwise the drawing is totally awesome!