There could be characters from other anime or manga universes. For instance, characters from 'One Piece' might show up. Luffy could be a really interesting addition as his carefree and adventurous nature would contrast with Naruto's more serious and duty - bound personality.
Perhaps Naruto forms new alliances in this 'naruto after the war crossover fanfiction'. He might team up with characters from other fictional universes who got involved because of the crossovers. They could work together to restore peace not just in his world but also in the worlds that have been connected through the crossovers.
One great aspect of 'Naruto Total War Warhammer Fanfiction' could be the unique character combinations. Imagine Naruto characters in the Warhammer universe, like Naruto using his Rasengan in the midst of a Warhammer battle. It would be a spectacle of different powers and fighting styles colliding.
Well, it could be about Naruto and his friends being transported to the Gears of War universe. They might have to fight the Locust horde using their ninja skills. Naruto could use his Rasengan against the tough enemies there.
One common theme is adaptation. Naruto and other characters have to adapt to the new world they are in during the crossover. For example, if it's a crossover with a modern - day world, they have to understand new technology and social norms.
Another possibility is that there is a new threat that emerges from the combination of the two universes. Some sort of evil entity that has the powers of both the Naruto universe, like the ability to use chakra, and the dark magic from the God of War world. Naruto and Kratos would have to learn to trust each other quickly in order to stand a chance against this new foe. They might start off at odds with each other due to their different backgrounds and fighting styles, but eventually realize that they need to work together.
One possible reason could be to protect his family. After the war, Naruto might have made many enemies. By faking his death, he could draw the attention of these enemies away from his family, especially his wife and children. His enemies would think he's no longer a threat and stop targeting his loved ones.
In some fanfictions, Naruto becomes more jaded after the war. He has seen so much death and destruction that he loses some of his initial idealism. He might be more cautious in his actions and less quick to trust.
In some fanfictions, Naruto and Hinata start a family right away. They enjoy a peaceful life in Konoha, with Naruto being a great Hokage and Hinata supporting him at home and also taking part in some village activities.
One common theme is rebuilding. After the war, the villages, especially Konoha, need to be rebuilt both physically and socially. Another theme is reconciliation, like Sasuke coming back to Konoha and being accepted again. Healing is also a theme, as the characters have to deal with the mental and physical scars of the war.