He could interact with his old sensei, Iruka. Iruka was an important figure in Naruto's life, and as a ghost, Naruto might visit Iruka to give him some comfort or to seek advice. Since Iruka was always there for Naruto when he was alive, their connection could still exist in the afterlife.
One possible plot could be that Naruto dies heroically in a final battle against a powerful enemy. As a ghost, he discovers that there are unresolved issues in the Hidden Leaf Village. He then tries to communicate with his friends like Sasuke and Sakura, but they can't see him at first. Eventually, he finds a way to make his presence known and helps them solve a mystery that was related to an old enemy's plot that was still endangering the village even after his death.
In this kind of fanfiction, Naruto might find himself in a whole new world as a shinigami. He could use his ninja skills in unique ways. Maybe he'd have new powers related to the shinigami realm, like controlling souls in a different way than he did as a ninja. He'd also likely encounter different challenges and enemies that are specific to the shinigami world.
One possible plot could be that Naruto, after dying heroically in his own world, is sent to the Soul Society. There, he discovers his new spiritual powers as a Soul Reaper. He might struggle at first to adapt to the new rules and hierarchy. He could meet old friends in spirit form and together they train to become strong Soul Reapers. Naruto's determination and unique ninja skills might give him an edge in this new afterlife, and he could end up facing some great evil in the Soul Society, using his newfound powers in unexpected ways.
In this fanfiction, Naruto's death could be a sacrifice. As a hollow, he could start off being very confused. His ninja skills might be warped in this new form. For example, his Rasengan could turn into some sort of dark energy blast. He might also meet other characters from the Naruto world who have also had strange after - deaths, and together they try to find a way to either move on or return to their normal state.
Perhaps it's a rogue Shinigami who doesn't want Naruto to figure out how to control his new form. This Shinigami might fear that Naruto could disrupt the balance between Hollows and Shinigami if he becomes too powerful in his hollow state. So, he tries to stop Naruto at every turn, creating a lot of conflict in the fanfiction.
If Naruto died and Sasuke became Hokage, it would be a very different Konoha. Sasuke, with his brooding and somewhat isolated nature, might rule with a more strict hand. He would likely focus on security and protecting the village from external threats. His past experiences with the dark side might make him extra vigilant. However, he would also have to deal with the loss of Naruto, his long - time rival and friend, which could add a layer of melancholy to his rule.
It could be a powerful Hollow that has somehow broken free from the normal Hollow hierarchy and is causing chaos in the Soul Society. This Hollow might have a special ability that makes it difficult for the Soul Reapers to defeat it, and Naruto, as the new Soul Reaper, has to figure out a way to stop it.
One possible plot for 'naruto becomes a ghost fanfiction' is that Naruto sacrifices himself to save the village. As a ghost, he discovers new abilities like being able to possess people or objects. He uses these powers to protect Konoha from threats that the living ninjas can't handle. He might also have to deal with his own unfulfilled desires and relationships in this new ghostly form.
The plot could involve Naruto being resurrected as a vampire by some dark magic. As a vampire, he is shunned by some in the village at first. But then he discovers that there are other vampires who are planning to take over the ninja world. So he teams up with his old comrades, using his unique combination of ninja skills and vampire abilities to stop them.