In some fanfictions, Naruto having Kyuubi's eyes could signify a deeper connection to the Kyuubi's power. It might mean he can access its chakra more directly or even gain some of the Kyuubi's abilities related to perception, like seeing chakra more clearly.
One interesting concept could be the Kyuubi eyes having unique powers like seeing through illusions that even the Sharingan can't detect. This would give Naruto an edge in battles against powerful foes who rely on deceptive jutsu.
Often, in fanfiction, Naruto with Kyuubi's eyes is shown to have enhanced abilities. Writers may show him using the Kyuubi's eyes to see through illusions more easily. They might also describe his vision as being able to detect the slightest movements or changes in chakra flow. His appearance could also change slightly, with the eyes being a central focus. Maybe his pupils become slitted like a fox's, which adds to his overall otherness. This new look could also attract different reactions from characters in the story, from admiration to fear.
Some fanfictions might depict the Kyuubi eyes as having a mind of their own. They could be constantly communicating with Naruto in a silent way, guiding his actions or warning him of danger. It's like they are a separate entity within him that he has to learn to work with.
The ability could also affect Naruto's power on an emotional level. Knowing that Kyuubi can see through his eyes might make Naruto feel more confident. He might be more willing to take risks in battles or in exploring new areas. This new - found confidence could translate into him using his existing powers more effectively, like his Rasengan or his ability to summon toads. Also, Kyuubi might be able to spot things that can help Naruto improve his jutsu. For example, if there are certain natural elements or energy sources that Naruto can use to power up his jutsu, Kyuubi could see them through Naruto's eyes and tell Naruto how to utilize them.
In some stories, the fox eyes might give Naruto a kind of hypnotic or intimidating power. Enemies might be momentarily stunned or less able to fight effectively when they look into his fox eyes. This could be a unique advantage in battles, allowing Naruto to gain the upper hand without having to use as much physical force.
In some fanfictions, Naruto's mother, Kushina, has a special connection with the Kyuubi. For example, some stories might explore how Kushina's chakra influenced the Kyuubi's behavior. Since she was the Jinchuriki before Naruto, her relationship with the Kyuubi could be a rich source of plot development in fanfiction.
His relationships with his friends might become stronger. Since he can see more clearly with his god eyes, he can better protect them. His friends would trust him more knowing he has this extra power to keep them safe.
One great fanfiction is 'The Fox - Eyed Naruto' on FanFiction.net. It really delves into how Naruto's fox - eyed appearance changes the way people perceive him in the village. The author does an amazing job of integrating this new physical trait into the existing Naruto universe storyline.
His relationships would become more complex. The villagers who once hated him for having the Kyuubi inside him might now be even more terrified as he has its soul. However, Naruto's friends like Shikamaru would likely see this as an opportunity for Naruto to grow even stronger. They would try to help him harness this new power while also making sure he doesn't lose himself to the Kyuubi's wild nature. This new situation would test all of his relationships.