Hey man, SICK painting! I love it. I did a quick paintover to highlight a few suggestions.
- Your lighting (on the girl and dragon) looks more like what you'd see from an overcast sky - not a lot of reflected light and not much color in the shadows. You could change the sky to overcast to fix this but I changed the lighting to match the sky.
- So, I added some blue reflected light along some edges of the dragon (mostly on the shadow side). I probably didn't really do this the right way but with some ref you can probably sort it out.
- Color shifted the shadows to be blue-ish. You'll see this from reflected light from the sky - the shadows are blocked from being hit by sunlight, but not reflected sky light.
- I like the girl's costume but generally I think the fabric may be a bit too tight - generally to would probably drape off her chest more and you wouldn't be able to see her rib cage (ref:
http://www.goodorient.com/images/D/GBL1007_1_main.jpg). Also silk has a shiny, reflective finish so you'd need to get some reflected light in there. I dunno if that ref is the direction you were thinking, though.
- Bumped up the contrast in the areas that are coming forward the most - girl, dragon head, dragon arms
- Added a bit of detail on focal point areas of the dragon, like the hands (mostly reflections - just dots really - on the details of the claws and scales)
- Brushed in some semi-transparent solid colors behind these focal point areas (on top of the parts of the dragon that are directly behind the head, hands, and girl) to make the focal point areas come forward more, and not get lost in the midground of the rest of the dragon.
- Made sure there were sharp edges on these focal points.
I don't know if my rendering skills were up to the task here, but hopefully some of this is helpful! Great work man!