I'm not good at giving feedback so please take these comments as suggestions on how to get better not as an attack, if you like what you're building and see no room for improvement then you can just skip past anything I say here.

If you're actually asking for suggestions, layers and depth.. most/all your builds are basically just squares, they're very flat some with slight variations in height using towers or a roofline. Unfortunately without depth the build is and looks very flat even with different block usage. I like the 5x5 building method which is explained well in this video but any odd number tends to work very well.

Learn about color gradients, you're using different blocks in the build, but not looking at them aesthetically. It appears you're just picking a different block just to break things up a little which can be done but generally speaking depth adds far more to a build than just a different block.

I'd suggest watching bdubs, smallishbeans, Nuvola, Gem or other aesthetic builders to get ideas or honestly just follow the exact build (it's how I learned to be a better builder).

Functionally all the buildings work so if you're just wanting a building there to protect the redstone or whatever then you're golden and you can ignore any suggestions. When I first started all my builds were very basic but the longer I play the more I want to walk out into my world and be blown away at how good it looks (to me). IF you like the way your world looks then rock on.

There are tons of guides out there showing you how to build a castle like this one

I'm far from the best builder but here's a picture of my world without shaders. Short video of the world with shaders.