A really unique concept is when Peter's consciousness gets split among different dimensions. So he has to find a way to reunite his consciousness while also dealing with the different situations in each dimension. For example, in one dimension he might be a wanted criminal, while in another he's a hero worshiped by all. This creates a lot of internal conflict for Peter as he tries to piece himself back together.
One unique concept could be the different dimensions Naruto might visit using the Rinnegan. For example, a dimension filled with ancient, powerful beasts that he has to either fight or form an alliance with. Another concept could be the alteration of time in these dimensions. He might experience time differently, like a day in one dimension being equivalent to a year in the Naruto world. Also, the idea of different chakra natures being dominant in various dimensions is interesting. In some dimensions, there could be a chakra nature that doesn't exist in the main Naruto universe, and Naruto has to learn to adapt to it quickly to survive and find his way back.
Well, in some fanfictions, Peter Parker is a blogger. He uses his blog to report on not just Spider - Man but also other superhero - related events and social issues in his city. It's a modern take on his role as an information spreader, different from the traditional newspaper photographer role.
One great Peter Parker dimension travel fanfiction is 'Across the Dimensions'. It shows Peter exploring different dimensions and meeting alternate versions of himself. The story has great action scenes and really delves into how Peter adapts to these new and strange worlds.
One interesting concept could be a Peter Parker who has mutant powers in addition to his spider - abilities. For example, he might have the power of telepathy, which could add a whole new layer to his crime - fighting. He could use it to anticipate the moves of villains before they make them.
There's a fanfiction concept where Peter Maximoff is a detective. His super - speed helps him solve crimes in ways no one else can. It's a really interesting take as it combines his abilities with a completely different genre.
In some Avengers dimension travel fanfiction, the idea of different dimensions having unique laws of physics is explored. This can lead to really cool scenarios like the Hulk's strength being affected in unexpected ways or Thor's powers working differently. It adds a layer of unpredictability to the story and makes it more exciting.
Another concept could be Naruto having to adapt to different power systems in the dimensions he travels to. Maybe in one dimension, physical strength is more important than chakra control, and he has to learn new fighting styles to survive.
Another plot is one where Mysterio fakes his death and then comes back to seek revenge on Peter Parker in a very elaborate and mind - bending way. The fanfiction plays with the idea of false identities and how far someone will go for revenge. It has Peter constantly on his toes trying to figure out what's real and what's not.
One interesting concept could be Demon Peter Parker's struggle with his new demonic nature while still trying to uphold his sense of justice. He might have enhanced powers that come with a dark side he has to control.
Some fanfictions play with the idea of power - swapping. Maybe a young hero from Young Justice gets the powers of a Justice League member and vice versa. It's a really cool concept as it forces the characters to adapt to new abilities and challenges, and it often leads to some really fun and unexpected storylines.