not sure what you mean by horror media but these are my recs for all things horror
Manga: Franken Fran and junji itos works if you want body horro. Hell Girl, Mieruko-Chan and Phantom tales of the night for supernatural horror. and tokyo ghoul, Higurashi or When they cry, Sugar Happy Life and Brutal: Satsujin Kansatasukan no Kokuhaku
Movies: Beyond the Darkness, Pieces, Terrifier and Audition for gore or extreme movies. Texas Chainsaw Massacre, American Mary, My Bloody Valentine, Black Christmas and Slumber Party Massacre I and II for slashers. Grave Encounters, The Autopsy of Jane Doe, Gonjiam Haunted Asylum, The Taking of Debora Logan, Possession, House of Seven Corpses, Candyman, House and As Above so Below for Supernatural. Boxing Helena, Tag, Little Shop of Horrors, Rocky Horror Picture show, Frankenhooker, Love Witch, Brain Damage, Basket Case, and Suicide Club for ones that idk what to put to them in.
Shows: What We Do In the Shadows, Hannibal, Buffy the Vampire Slayer
Anime: Perfect Blue, Blood-C, Wonder Egg Priority, Another, Future Diary, Angels of Death, Future Diary, Paranoia Agent, Ergo Proxy, Parasite and Inuyashiki
Books: Heart Shaped Box by Joe Hill, Ring and Dark Waters by Koji Suzuki, Exquisite Corpse and Lost Souls by Poppy Z. Brite, Flesh Gothic by Edward Lee and Audition by Ryu Murakami
Songs: Anything from Creature Feature like Buried Alive, Carpe Demon, Six Foot Deep and Wake the dead. Some songs from Insane Clown Posse like Cemetary Girl, Ol' Evil Eye, and In My Room.