make lots more of these layers and merge them to random pattern for a wall
step 4 of 9
added some windows border and then transformed them into a rectangular shape. cut the corner part and enlarged a little bit for a little tower.
step 5 of 9
added some shadows and perspective into the wall as well as another tower
step 6 of 9
added a pond and the reflection of the castle
step 7 of 9
created some sky background
step 8 of 9
Added a hill and some trees and plants for some background to the right. The hill is just a shape with a dark brown and the trees are from one of my images (see source link). The shrubs have been created with a brush in Photoshop.