Well, a cool concept in Naruto face mask fanfiction could be a cursed face mask. It might be discovered in an ancient ruin and when worn, it slowly starts to take over the wearer's mind, making them act more like Naruto's darker side. Maybe it was created by an old enemy of the Uzumaki clan. Also, a face mask could be a key item in a time - travel fanfiction. A character finds a Naruto - themed face mask and when they put it on, they are transported to different eras in the Naruto universe.
One interesting concept could be a story where Naruto has to draw Kakashi's face as part of a training exercise. He struggles to capture the mystery and calmness in Kakashi's eyes. Another could be a time - travel fanfic where Kakashi's face in his younger days is a key element in changing the future of the ninja world. For example, someone from the future sees Kakashi's face in an old photo and realizes a connection to a major event that needs to be altered.
There could be a fanfiction where an enemy uses a special oxygen - mask - related jutsu. For example, they create a poisonous gas and the only way to counter it is with a special oxygen mask that has unique chakra - infused properties. In this fanfiction, the search for these masks and the race against time to save the village would be exciting plot points.
One interesting concept could be a crossover with a horror game like Silent Hill. It could create a really spooky and complex universe where the eerie atmosphere of both games blend. For example, Sally Face's unique art style and the psychological horror elements could interact with Silent Hill's fog - covered, nightmarish town setting.
One interesting concept could be that Naruto's wings represent his newfound freedom. Maybe after a great battle or a personal transformation, the wings emerge as a symbol of his ability to soar above his past troubles. He could use them to travel faster between villages, or in combat, he might use the wings to perform unique aerial jutsus that no one has ever seen before.
One interesting concept could be Naruto unlocking a new form related to dragon chakra. Maybe it gives him the ability to fly like a dragon and breathe some sort of elemental breath. Another could be that the dragon chakra has a connection to an ancient and powerful dragon spirit that guides Naruto in his battles.
One interesting concept could be Naruto having an unexpected form of spiritual pressure that gives him new abilities. For example, it might enhance his shadow clone jutsu in a unique way, like allowing the clones to have a sort of spiritual echo that can confuse enemies.
One interesting concept could be a crossover where Naruto's father, Minato, and Erza's father (if he was alive in a different way) meet. Maybe they could team up to train Naruto and Erza in some super - secret combined ninja - magic techniques. Another idea is that they could be from parallel universes and the fathers have to figure out how to get their children back to their respective worlds.
One interesting concept could be Naruto being transformed into a half - cat form with cat ears as part of a jutsu gone wrong. This could lead to humorous situations as he tries to adapt to his new appearance, like constantly getting distracted by shiny objects or having an urge to chase mice.
One interesting concept could be how a character might inherit or interact with the Rikudou Chakra in a new and unique way. For example, they could gain powers that are a combination of the different aspects of the Rikudou Chakra, like having the ability to create life - like Hagoromo was said to be able to - in a small way, such as growing plants instantly. Another concept could be a story where the Rikudou Chakra is misused and creates chaos in the Naruto world. This could lead to a hero's journey to set things right.
Some fanfictions might explore the idea of Naruto befriending an Espada. This friendship could lead to Naruto learning about different ways of combat and power management from the Espada. It could also result in the Espada having a change of heart due to Naruto's positive influence, and together they could face new threats in the Naruto universe that neither could face alone.