I really love how you did those curved corners, those have always been a weakness for me. I can see why you want color, though. While it is a good build, it needs zest! I always liked using fountains, and since this is vampire-focused, try maybe using some dragon busts/statues made from netherbricks and add some custom trees as well. Here's some screenshots of a vampire/dragon castle I was working on:
I admit I used some youtube videos and pictures for inspiration of the dragon busts, but I can link those if you want! If you are considering doing some roofs for hallways, I would recommend netherbrick or spruce/dark oak. But definitely add some greenery (or some dead trees with cobwebs or even mushrooms if that's possible). Banners would look nice, along with fire brazers (these would be awesome to include). Here's a lantern I built and used to hang around my place:
So by adding some lanterns lighting up a path rounding around the structure with some hedges along with some fountains (water or lava), you could potentially make it all really pop!
P.S. If this is going in Essalonia, I highly recommend a dungeon/sewage access point into the sewers somewhere in or around the build. The Essalonia Collective thread on the forums are organizing roads between factions, with maybe sewers being added underneath all across the map for vampires/slum roleplay.
