I like the sense of scale, with the figures being small, next to the large dragon, with mountains beyond! Also, the detail on the dragon is excellent.
I do think that the picture does not feel like a whole - the dragon is much more detailed than either the humans or the mountains: some of the snow on the mountains looks like just quick brushstrokes. That can work in some pictures, but it doesn't seem to mesh in this one. The dragon also seems more in focus than the humans- perhaps because it has harder edges and brighter colors, plus the added detail? Also, my eyes almost lose the top of the dragon's head against the rocks and snow behind it - the snow and the horns are about the same value. I think that maybe if it was darker behind the head, without as many of the rock shapes in THAT area, it would read better. Either that or add a rim highlight to the horns.
I like the look of the mountain in the distance, with the clouds around it.