One common theme is friendship. Writers might explore how Nim and Edmund form a strong bond. Another theme could be adventure, with them going on exciting quests together.
Sure. One popular Nim Edmund fan fiction might be found on fanfiction.net. You can search there using the keywords 'Nim Edmund' and explore different stories written by various authors.
One idea could be that new, mysterious creatures arrive on Nim's Island. Nim has to figure out where they came from and if they pose a threat. Maybe they are friendly but misunderstood, like the new animals could be some kind of magical beings that only come out at night and Nim has to learn their language to communicate with them.
Nim herself is of course very interesting. You can explore more of her inner thoughts and her relationship with the island in different situations. Her father also makes for an interesting character. You could write about his adventures before coming to the island and how those experiences shape his relationship with Nim. Jack, from the movie, can also be included. He could come back to the island with new stories and challenges for Nim.
This book was called "Nightmare Erosion." The characters in the book included: the main character-Eater, the hidden true main character; the supporting character-Dr. Willy, the inventor of the God-Slaying Battle Armor; the male character-Loen, who relied on his father to make a living; the male supporting character-Nim, who was obviously the main character; and the female supporting character-Dai Linna. Could it be that I wasn't the female lead? This book can be read on Qidian Chinese website.
"Nightmare Erosion" Author: Very Sweet Salted Fish. It is a fantasy/alternative fantasy novel with transmigration, invincibility, and Cthulhu elements. It is finished and can be enjoyed without worry.
User recommendation: Immortal Grass
Cthulhu's style of writing. There's nothing I can't eat.
I hope you will like this book.
One popular example could be 'The Proud Family'. It showcases a range of characters and has storylines that appeal to a wide audience. Also, 'Little Bill' has some cute black girl characters that kids enjoy.