This castle was originally intended to be used in a larger diorama, but it turned out to be too large. At 5x5 studs, this might say more about the diorama than about the castle.
Putting the castle into a 8x8 vignette, gives some nice context and the ship approaching the castle aids in conveying size.
I guess an LDD model could be considered cheating, but at least all parts are guaranteed to be valid and available from pick-a-brick. See the page on MOC Pages
for the LDD file.