Stefan Salvatore is one of the main characters in the Vampire Diaries novel. He is a vampire with a complex personality. He struggles with his vampire nature, often trying to resist his baser instincts. He is in love with Elena and his relationship with her is a central part of the story.
Caroline, for example, might be more accepting as she is also a vampire. She could help Elena adjust to her new life. Damon, on the other hand, might be jealous or feel threatened that Stefan made Elena a vampire. It could change the power balance between the three of them.
In the TV show, Stefan is played by a particular actor, which gives a visual representation. In the novel, readers might have a different mental image of him. Also, the TV show might have added some plotlines for dramatic effect that are not in the novel. For example, some relationships might be developed differently in the two versions.
One great fanfiction is 'A New Beginning for Stefan and Elena'. It explores a different path for their relationship after the events in the show, where they face new challenges together in a world filled with both old and new vampires. It's a really interesting take on their relationship and shows a more mature side of their love.
There are also fanfictions that focus on the power dynamics between them. As a vampire, Stefan has certain powers, and how that affects their relationship, whether it creates a sense of imbalance or a unique bond, is explored. For instance, Stefan's ability to protect Elena with his vampire strength can be a central plot point in some fanfictions.
Perhaps Stefan gets hurt in a race against time. He's trying to stop a spell from being cast that would endanger the whole town. But in the process, the caster of the spell manages to harm him. Elena would be desperate to save him, and she might turn to some of her own latent powers (if she has any in the fanfiction) to heal him. The Salvatores' relationship would also be put to the test as Damon blames himself for not being there to protect Stefan.
A fanfiction where Stefan gets hurt could start with him being lured into a trap by an old enemy. They manage to wound him badly using a weapon made of a special material that weakens vampires. Stefan would be in pain and his brothers and friends in the Vampire Diaries world would have to band together. Bonnie could use her magic to try and heal him while Damon plots revenge against those who hurt Stefan.
I really liked the fanfiction 'Stefan and Caroline: Unlikely Allies'. In this one, they start off as just friends trying to solve a mystery in Mystic Falls. But as they work together, their feelings start to change. It's interesting because it focuses a lot on their personalities and how they complement each other. There are some really good action scenes too, which makes it more exciting.
One popular fanfiction could be about Valerie and Stefan's secret meetings in the woods. Maybe they share a deep connection that was hidden from others in the series. They could be exploring their feelings for each other while also dealing with the chaos of the supernatural world around them.
The theme of 'power couple' is also quite common. Fans like to write about how Caroline and Stefan, with their combined strength, intelligence, and vampire abilities, can take on the various threats in Mystic Falls. They become a force to be reckoned with, and these stories usually have them saving the day in spectacular ways.