Aright first thing I wan't to say is that this is a difficult piece to critique for 2 reasons, your art style makes it hard to tell what is supposed to be detailed or not, and its fantasy so its difficult to tell what I am looking at, but hear it go's.
Aright over all I love this piece the color's are very complimentary, it inspires a good Awe feeling, and even though you didn't use much detail you can still get a very good idea of what is going on.
Now as for the nightie gritty, the beach area(at least I think its a beach) in-front of the toad is a bit hard to distinguish from the cliffs around it, either make the detail more curved, sunk in as if its eroded or sandy; Lack of that ta heck with the beach and make it just as the cliffs around it. there's, also that corner on the bottom left side where you just left the outer edge just flat and rigged; Don't do that, at least make it foggy or broken up by other details, otherwise it just kills the whole fantasy effect of the art. other than that some ambient affects would be nice, fish in the water, mossy rocks and grass that sorta thing. O also the pilings on the dock would go above the dock itself, or there would at least be cleats to tie your boat off on, because there's noway anyone would ever tie off under the dock, just wouldn't happen.
Well, I hope it helps. I'll be looking out for ya.