Naruto's relationship with the new generation of ninjas would be interesting. They've only heard stories about him. His resurrection would make him a sort of legend come to life. Some might idolize him immediately, while others might be skeptical. He would have to earn their trust and respect all over again, and in the process, he could form new and unique relationships with these young ninjas.
Well, a plot twist might be that Naruto's resurrection is part of a grander scheme by an old enemy. This enemy brought him back not out of kindness but to use him as a weapon. Naruto, being Naruto, would then have to fight against this control while also dealing with the changes in the ninja world since his death.
Perhaps Naruto is betrayed by someone he trusts deeply. This person leads him into a trap at the Valley of the End. Naruto, being caught off - guard, is fatally wounded. His death in this fanfiction could be a tragic end to his journey of becoming a great ninja and a symbol of how even the most powerful can be brought down by treachery.
I'm not sure of a specific title off - hand, but you can often find great ones on fanfiction websites. Look for ones with high ratings and lots of reviews. They usually are the better - written ones.
Madara Uchiha might be the main antagonist. He has grand plans for the ninja world. He could see Naruto as a threat to his vision and engineer a situation in the Valley of the End where Naruto is killed, either directly or by using Sasuke as a pawn.
Perhaps in this fanfiction, Naruto is fatally injured by a powerful enemy who has lured him to the Valley of the End. He's outnumbered and despite his best efforts, he succumbs to his wounds. His death then has a profound impact on all his friends and the entire ninja community, leading to a new era of unrest and a search for a new hero.
Sasuke could be responsible. Their relationship has always been complex. Maybe in this fanfiction, their rivalry escalates to a point where Sasuke accidentally kills Naruto during a fight at the Valley of the End.
One possible plot could be that Naruto is resurrected by a powerful and mysterious jutsu. He then has to deal with a new threat that emerged while he was gone. He reunites with his old friends and they train together to face this new enemy.
The main characters would surely be Naruto and Sasuke. Their final battle at the Valley of the End is a crucial part of the Naruto story. However, in a fanfic, characters like Itachi could also be brought in. His influence on Sasuke and his actions in the overall Naruto plot could be explored in relation to the Valley. And don't forget about Jiraiya. His teachings to Naruto could be revisited and related to Naruto's experiences in the Valley of the End.
One idea could be a what - if scenario where Naruto and Sasuke have a rematch at the Valley of the End years later, but this time they have to team up against a new, powerful enemy that threatens the entire ninja world. Another could be a story exploring the emotional aftermath for Naruto if he had actually killed Sasuke during their fight there. Maybe a fanfic where the Valley of the End becomes a place of peace and training for future generations of ninjas.