A few suggestions: On the trees redo the mesh texture for the leaves and make the brances a bit thicker they dont really show up in the foreground trees. Raise the frequency of the castle wall texture to make it appear more realistic and distant, same deal with the other textures on the castle. Vary the hieghts of the towers, not many castles are completely symmetrical Maybe darken the sky a little The concept is awesome, but you asked for some constructive cristizism and there it is. Re-post the work when yo uhave made corrections I would love to see the final version!