One idea could be Naruto traveling to a dimension where all the villains have become heroes. He has to adapt to this new world order and figure out how to get back to his own dimension.
Another plot could involve Naruto finding himself in a dimension where the Akatsuki are the protectors of the villages. He is initially suspicious but then realizes that there are greater threats in this dimension that made the Akatsuki change their ways. He then has to team up with them to face these threats, all while trying to understand the different relationships and power dynamics in this new dimension.
One idea could be Naruto getting trapped in a dimension where chakra doesn't exist, and he has to learn new forms of power. Another could be a dimension where the Akatsuki are the heroes, and Naruto has to figure out how to co - exist or change that world. Or perhaps a dimension where all the dead characters are alive again, but in different roles, like Itachi as a rogue ninja fighting against Konoha.
One idea could be Naruto being transported to a dimension where chakra doesn't exist, but he discovers a new form of energy and has to learn to use it from scratch. This would force him to adapt his fighting style completely.
One interesting plot could be Naruto traveling to a dimension where the Akatsuki are the heroes. It would be a complete role - reversal, and Naruto would have to figure out how to interact with them. Another could be a dimension where everyone has a different type of chakra, like water - based chakra for all shinobi, and Naruto has to adapt his skills.
One idea could be that the main character accidentally activates a forbidden jutsu that transports them to different dimensions in the Naruto universe. For example, they might end up in a dimension where the Akatsuki has successfully captured all the tailed beasts and rule the world. They then have to find a way to team up with some of the remaining shinobi to reverse the situation.
One idea could be that Naruto travels to a dimension where all the female characters from different Naruto arcs are united. They all fall for his unique charm and his skills as a ninja. He has to balance his new relationships while also finding a way back to his own dimension.
One idea could be Naruto arriving in a dimension where chakra doesn't exist and he has to learn new powers. Another could be him meeting alternate versions of his friends in different dimensions, like a super - evil Sasuke in one dimension. Maybe he also discovers a dimension where the Akatsuki are the good guys and he has to figure out how to work with them.
A really exciting plot could involve Naruto getting trapped in a time - loop within the Juubi dimension. Every time he tries to find a way out, he ends up back at the starting point. He has to figure out how to break the loop by solving a mystery related to the Juubi's power. This would require him to interact with different versions of characters he knows, who may have different personalities and motives in this strange dimension.
One idea could be that Peter discovers he has special powers in this other dimension that he doesn't have in his own world. For example, he can control elements like fire or water. Another could be that he meets alternate versions of his friends and family, and has to deal with the differences in their personalities. Maybe in this dimension, his best friend is his enemy.
In an 'Avengers Another Dimension Fanfiction', a cool plot might involve a dimension where technology and magic are one and the same. So Iron Man's suit could be powered by both arc reactor energy and some sort of magic spell. Or a dimension where the Avengers are part of a gladiator - like arena, and they have to fight not only their usual foes but also other heroes from different universes just to survive and find a way back home.
One idea could be that the characters from different dimensions team up to fight a common enemy that threatens all dimensions. For example, Yugi and his friends could join forces with counterparts from a dark dimension who have their own unique cards and strategies. This would lead to some really cool duels and character interactions.