I have a few suggestions that you may find useful, I mean no offence and if you feel the need too you can critique me its cool. I just know all too well what its like trying to get real feedback on sites like this.
Firstly the perspective between the castle in the mid ground and the people in the background on the steps is off. You can fix this by just making the castle a lot larger (maybe even covering that area behind the wizards flag) Second I would lose the characters in front of the wizard and extend the the brush you see on the left (maybe even replace the grass with rock or sand to better go with the colors you have chosen for everything else). Also I would vary up the size relationship in the rocks below the castle (rule of thirds idea) Lastly I know the castle is being lit by the sun but feels as though it itself is glowing. You can change this by playing with the curves layer in photoshop and masking things out and painting it back in. Also here's a link to Jaimie Jones's brushes, I think he has a really good brush for creating fog somewhere in there.
you're create a ambiance! the details and color so realistic I know an artist who don't be enough famous, so i do promoiton for him this is his birthday so just see comment and watch if you want those two last works : [link] [link]