There are many. For example, some fan fictions might focus on the backstories of minor characters in 'Boku no Hero'. They could explore how these characters got their quirks or what their lives were like before joining the hero academy.
Fanfiction.net is also a great place. There are many users who contribute their 'boku no hero' fan fictions there. You can search by category, like adventure or romance within the 'boku no hero' section. However, the quality can vary, so you might need to read a few to find the really good ones.
One interesting crossover could be the sharing of powers. For example, Spider - Man's web - slinging ability combined with a hero from Boku no Hero Academia's unique quirk. This could lead to new and exciting combat styles.
The Boku no Hero manga is finished. It reached its conclusion after a successful run, leaving fans with a complete narrative and memories of an exciting journey.
Fan - made art can also inspire new fan fictions. When an artist creates a really cool piece showing Spider - Man and a Boku no Hero Academia character in a new situation, it can spark ideas for writers. They might then write a story based on that art. Also, it helps to build a community. People who like the art will gather and discuss it, which in turn promotes the fan fiction genre.
Well, 'boku no hero novel' is probably about the adventures in the world of heroes. It could have new storylines that didn't make it into the main anime or manga. It may focus on a particular character's growth, like Midoriya's journey in a different light, or introduce new characters and their unique quirks within the hero - filled universe.
One popular idea could be creating an alternate origin story for a character. For example, giving Deku a different quirk acquisition experience that still leads to his growth as a hero.