Too much hill

You should crop off some of the hills. Or if your trying to make the castle seem small compared to the hills, you could at least put more detail on the hills closest to the castle to bring attention to the focus of the picture. And resize the image, it's way too big.

Great job!

You seemed to have accomplished your goal of making the castle stand out~
I like it~

Two models...

It looks like you have two separate models that you mashed together. The landscape is very nice, and dreamy. The castle has wonderful details and is a nice style. However, they don't match at all.

We see tiny windows on the castle, and yet the landscape doesn't contain a single rendered feature except the road. No trees, no shrubs, no rocks, no indication at all that it's made of something more than jello. The mountains, similarly, look like an angry tsunami about to crash on the castle. The effect would be riveting if the castle also looked so impressionistic. There's glow on the landscape, but no glow on the castle. The castle is not antialiased and doesn't look blended into the picture at all. Shadows, color scheme, everything make the image look like there is a castle in one universe and a landscape in another, and the fact that they are together is an aberration.

Serioulsy, re-render the castle on a white background. Post that on NG: it'll get good reviews. Then, take that image, and smear and blur the heck out of it in Photoshop (or GIMP if you like open-source), and then paste it back onto this green landscape. You'll have two images: the crisp and the dreary. Each will look better for it.