A fanfiction could focus on the backstory of a minor vampire character in Vampire in the Garden. For example, how they were turned and their struggles to adapt to the vampire lifestyle while still having some remnants of their human emotions.
Another interesting idea is a fanfiction where the main characters from Vampire in the Garden find a way to create a peaceful co - existence between humans and vampires without the need for the garden as a refuge. It could explore the challenges and triumphs in building this new world.
You could also consider a crossover with a detective - based series like 'Detective Conan'. The mystery - solving aspect of 'Detective Conan' could be combined with the complex and often mysterious events in 'garden of sinners'. The characters from both could work together to solve cases that involve both the normal and the supernatural.
Another interesting angle is to focus on the side characters. You could write a fanfiction about the Woodsman's past. What was his life like before he got trapped in the never - ending task of keeping the lantern lit? It could be a tragic love story or something related to his family.
One idea could be a vampire who is drawn to the lead singer of a rock band in 'Gravitation' due to the passion in their music, which is like a siren call for the vampire. Another could be a vampire that uses their powers to help the 'Gravitation' characters achieve their dreams in the music industry in exchange for small amounts of blood. Maybe a vampire who was once a famous musician in the past and now finds a connection with the modern music scene in 'Gravitation' and falls in love with one of the characters.
One idea could be Ranma turning into a vampire instead of a girl when splashed with cold water. It would add a whole new twist to his already chaotic life. He could struggle with his new vampire instincts while still dealing with his fiancées and martial arts rivals.
One idea could be a story where Elena discovers a long - lost relative who is also a powerful vampire hunter. This relative tries to turn Elena against her vampire friends, creating a lot of internal conflict for her.
One interesting idea could be exploring the backstories of the minor characters more deeply. In the fanfiction, they might give a detailed account of how a particular vampire was turned and what their life was like before. Another idea could be alternative relationships between the characters. For example, a fanfic might explore a different kind of bond between Louis and Lestat that wasn't fully shown in the show.
Well, you could write about a revival of the magic in Mystic Falls that has some unforeseen consequences for the vampires. Maybe it makes them more powerful than they were before, but also more vulnerable to certain things. Or perhaps a revival of an old vampire clan that challenges the existing power dynamics in the town. It could be interesting to see how the main characters deal with this new threat and how they adapt to the changes.
One interesting idea could be the different powers vampires have in the Undertale universe. For example, they might have unique ways of using magic that are related to their vampiric nature, like blood - based spells. Another idea is the interaction between vampires and the regular Undertale characters. It could lead to some really cool storylines, like a vampire befriending a monster or a human from the original game and having to deal with the differences in their natures.
Another idea is a love story in the 'shake it up vampire fanfiction'. A human dancer falls in love with a vampire who is secretly watching the dance shows. The conflict between their different worlds, the vampire's nocturnal nature and the human's normal life, can create a lot of drama and tension.
One idea could be that Merlin, as a wizard, is hunted by vampires because his magic is seen as a threat to their existence. But then he discovers that some vampires are not as evil as he thought and they form an uneasy alliance to fight a common enemy, like a dark sorcerer.