The castle of your dreams.

I actually like all the castles offered in the game, and I wouldn't remove any of them. Regarding adding something... Hmm... perhaps we could come up with something like a sea castle... As for monsters, let's say mermaids, sharks, crabs, giant squids, octopuses... crocodiles... Maybe we could add a unique feature to the castle, like their water spells getting a bonus. I think that's all I would add.