Breath of Smoke

The contrast is fine in my opinion; personally I feel that it adds to the effect that you're going after. The dragon looks as if it's made out of smoke itself, which I assume is the intended impression.

I just love how it's all faded into the dark background, but at the same time it's able to stand out - the smoke from the nostrils especially.

However, I feel that perhaps you could improve on the mouth-area, where the teeth seem broken-up almost. Perhaps the dragon is old and I'm very wrong, but I feel that it would be better.

Otherwise, a really good painting. Especially for a speedpaint, or something that's "nothing special" according to your description. It's earned a favourite from me, good job!