There's a time and place to use selective outlining effectively, and it's not for a still image on a light background. The only time it's necessary is when the piece will be moving along various backgrounds. Selout is basically anti-aliasing to a background of medium luminescence, so using a light background to show the dragon is just hurting the piece. Also, there's a uniform texture throughout the tree and dragon. Smooth. Trees have holes, disfigurements, peeling bark, perhaps cracking or bending from stress of the dragon's weight. You'll have to do more than spot it with single pixels to add any realistic texture to it. The pillow shading, especially noticeable on the trunk, doesn't help the lack of texture either.
The rocks are also rather smooth, but I'm more concerned about how they're stacked. They're all in the foreground. There's not pile of rocks to support the precarious tower of rocks shown. I'd like to see a sturdier base of rocks, to make the situation more realistic.
A similar occurrence happens in the tail feathers(?). Each one appears to be on the same plane as the rest, making them flat.
I can't stress depth and texture enough for it.