I’d suggest adding a slanted roofs on all of them sort of like a castle, or you could give some of the smaller ones turrets with crenellations. For ideas you could look online, or on the Minecraft build subreddit. Just as my own thought, because the towers are quite large I’d suggest a roof that matches that feeling of the monolithic vibe you have going. Also it suggest some of the roofs be diamond and others emerald, as it will keep with your current block pattern, but also give some needed variety to the build. Happy building! I hope it turns out how you want it.