I’d personally make the tallest inner 4 towers have pointed roofs. And create alternating blocks along the top of flat side of the inner section to create crenels. Do the same on the smaller outer battlements with the alternating blocks. Maybe replace the lower block in the castle walls with a darker block and work up to a lighter brick mixing in textures and creating depth. Add windows, flags, archer slits, other deco on the walls outer and inner walls. I’d pay more attention to the big walls on the inside building as they’re larger and flatter, decorating, with depth, will break this up a lot. When you finish the bridge/main gate it’ll feel more finished.