Maybe Zelda doesn't care for her royalty, but a castle is the home of a family for many generations. Her predecessors have put in some decorations. Your castle as it looks now is more like a gangs hideout. Wild growth and barely a decoration. In the attachment I've marked some changes that might be usefull.
1) The castle gate is not attached to the castle. At the place of the red square should be some additional gates. Or the secret entrance under the rocks in the corner doesn't serve a purpose. Or with the secret entrance in mind, you need move the gates.
2) Your castle does look like a cube. It isn't that bad, if you add some variation to the form. For example put towers on the corners of the walls.
3) The look of your castle is plain and looks nothing more than fortress for thugs. Even if Zelda doesn't care, her predecessors might have cared and the big guys in her staff also might care. So give it some more decorations. Put some statues at the front entrance and on the second level. You don't need to use Zelda statues, but some may be nice. Put the trifoce symbol on the walls on the second level and maybe even on the walls outside. Because you do want the outside people to know that this castle is home to the royal family.
Some flags and banners are a nice addition to the castle.
4) The garden looks a bit like Wild growth, instead of a garden. My advice is to remove the stone floor tiles (only leave them in the path to the door). And put some structured flower beds and plants there. A tree or two isn't bad, but it does fill the garden. Maybe put in some color next to the oh so dark castle walls.
I hop
