In many fanfictions where Peter's identity is revealed, it often leads to a whole new set of challenges for him. His friends and family might be in danger. For example, in some stories, villains target Aunt May to get to Peter. This forces Peter to be more protective and also changes his dynamic with his friends. They might either support him wholeheartedly or be scared of the danger he brings.
Often, Peter has to face new enemies. Since his identity is out, villains who were previously afraid of him being anonymous now come out of the woodwork. They see it as an opportunity to take him down when he's vulnerable.
One interesting plotline could be Peter's friends and family adjusting to his secret identity. For example, his aunt May might have a mix of pride and worry. Another could be how the public reacts. Some might see him as a hero, while others might fear his powers. And a third plotline could be Peter dealing with villains who now know his true identity and target his loved ones.
One common theme is the struggle for normalcy. Peter still wants to have a normal life but his revealed identity makes it hard. Another theme is trust. He has to figure out who he can trust now that his identity is known. And finally, there's the theme of responsibility. He has more responsibility not only to protect the city but also to protect those close to him who might be in danger because of his revealed identity.
Perhaps there's been some sort of miscommunication or misunderstanding among Peter and his friends. Maybe a villain has manipulated the situation in such a way that his friends now think Peter has betrayed them, so they've cut off all ties with him. This would create a very lonely and difficult situation for Peter in the fanfiction.
Fanfiction about Peter and MJ in the context of Spiderman and Spiderwoman often plays with different timelines and universes. For instance, there could be a fanfic set in an alternate universe where MJ has superpowers too. This would change the dynamics of their relationship completely. Writers can also explore how Peter and MJ interact with Spiderwoman in these fictional stories.
Perhaps Peter is alone in a forest, away from the city. He's there to find some peace and quiet, to get away from the chaos of New York. While he's alone, he reflects on his powers and how they've both blessed and cursed him. He might even start to train in new ways, using the seclusion of the forest to his advantage.
He might throw himself more into his superhero work. Since he has no friends to spend time with, he could use the extra time to patrol the city more often, stop more crimes, and focus on protecting the innocent.
In fanfiction, Peter Parker's scars as Spiderman could be a symbol of his battles and growth. They might be from fights with villains like the Green Goblin. Maybe a deep gash on his arm is a reminder of a narrow escape. Writers could use these scars to show his vulnerability and how he overcomes it each time he suits up as Spiderman.
One common theme is the exploration of their relationship. Since Peter has his double life as Spiderman, how that affects their relationship is often explored. For example, in many fanfictions, Michelle has to deal with Peter's sudden disappearances.