This is a beautiful piece. The detail in the dragon and the girl is absolutely amazing. However, the part of the dragon's tail right after the (backpack thing?) is not detailed enough (needs more contrast/shading) and there is a flaw where the tail begins to curve up towards the end where the line work loses some of its value. The mountains are so-so. And the muscle in the dragon's back leg looks a little odd when you look at it for a few seconds. The fur on the hind feet looks a bit out of place.
Overall you did a great job. I'm just pointing out the little things.
As mountains... they're not so great. As random boulders on a desert plain... they are really well done.
I like the dragon and the detail of its equipment with saddle and harness. The girl is well done as well. It must be a really tame dragon because I don't see the girl being able to stop it if the dragon decided to do its own thing.