Cool
Overall, I like the detailing you put in the dragon, it has good-looking scales and you come a great bakground.
But when I looked closer at the picture, the background was blurred a little and the dragon put on it made it look like a collage. Plus the posture looks a little weird to me, maybe you could have raised the lower back a little more. and the tail looks unrealistically crooked, if it was curved a little more, it would seem a little more suited. The wings also could have been lower down the shoulders, it looks like they are positioned on the top of her neck. The colour doesn't match too well either, a camoflauge green, red, or dark yellow would be a good choice.
I personally don't like the hair, it seem extreamly unnecessary (that's me, I dislike it on most animals people draw) Frill or spikes coming down would be a personal preference, in case you wanted to make a single person happy :P I'm not sure what you meant by "To keep warm" but frankly, dragons are lizards and spending a litte time in the sun would definately fix that.