I don't know what the rest of the map should be, but please do take these into consideration.
Include some sort of abandoned Cathedral. Make the map dark, and the colors dull to fit in, make the Cathedral seem pointy, sharp, menacing, intimidating, but not demonic.
Add some broken areas to it. Blood if you wish, cobwebs, a dungeon-like or labyrinth-like basement, large, mossy and stone gray brick, very little lighting but enough like at long hallways (At corners). What is at the end of the labyrinth is your choice.
These are just some Ideas I think would make it look loving awesome. The cathedral isn't the ONLY thing though, but definitely add this in as well as something else, maybe a graveyard? Or or ruins of Catacombs, bombed with cobwebs and decayed stone under the graveyard.
(With a small building in the graveyard, stairs leading down descending a long way, or not, or a short way, leading to a tan light, tan stone catacombs lit by torches. Very few for eerie lighting.)
I really hope you read this. I think these are some interesting ideas. And would make for some awesome secrets.
