In many aspects, 'Across the Spider-Verse' adheres to the comic book canon. However, there might be some creative liberties taken to make the story more cinematic and engaging for the audience while still respecting the core elements of the comics.
It's a story about Miles Morales. He's a Spider - Man from his own universe. In this movie, he travels across different spider - verses. He meets various versions of Spider - Man and Spider - Woman. There are cool action scenes and a lot of character development as he tries to find his place among all these different spider - powered heroes.
One interesting storyline could be an OC with a unique spider - power, like the ability to turn invisible. They could team up with Peter Parker to take on a new villain in the Spider - Verse. Maybe this OC has a personal vendetta against the villain that adds an extra layer of drama to the story.
A Peter Parker OC can fit into the world by having a specific role or mission. Say, they are on a quest to collect fragments of a powerful artifact that has been scattered across the dimensions. This mission brings them into contact with Peter Parker and the other Spider - people. Their unique skills and abilities related to this mission would contribute to the overall plot and make them an integral part of the fanfiction.
One great 'Across the Spider - Verse Fanfic' is 'Spider - Verse Bonds'. It focuses on the relationships between different Spider - People. It shows how they interact, support each other, and grow together in this multiverse. It has really engaging character development.