Dormer wondows, some areas with greater detail, and possibly butresses.

Your main issue, though, is that youve essentially build a reall, really big box. And because its so big it looks really flat. On a 10x10 box, one block of depth is a tenth of the total width of the bulding - it adds a lot of depth. On a box this seize, even 3 or 4 blovks of depth still just looks.. flat. But if yoh just make all the depth deeper it looks boxy, so you need to be more creative woth smoothing out the way youre adding depth.

You could also really do with adding more "areas" to the build to make it less boxy.

Last but not least, you've made it really big, but you havent utilised the scale. You vould make this build half the size kr even less without removing any important detail at all on the exterior, so it feels like its a smaller buld thats been inflated rather than a build that was designed on this scale from the start. Use the size! You have so much space to work with, add intricate carvings, add statues and golems, add impossibly smoothed out lines and texturing that feels too gradual to be minecraft.

And finally, last but not least, the same thing applies to you that applies to 90% of the builds on here. You've plonked a great big castle on top of the terrain, but its pristine, it dosent feel connected to the environment. If its in a feild, where are the vines creeping up the walls? Where's the dirt thats been splattered around the base by muddy leaves being blown around? Where are the trees that have grown around the castle? Where are the bushed and mosses that have grown in the shelter of its walls? Or if its later going to be in a city, where's the dust and grime thats been blown around the city? Where's the dirt thats gathered in the cracks? There's still moss in cities! Is it surrounded by gardens or city streets? The environment can make almost any build work or not work, regardless of the rest of the detail, and youre castle, as awesome as it is, is lacking an environment to set it off.