One idea could be to set the story in a modern corporate world where the different houses are rival companies vying for market dominance. For example, Stark Industries could be a tech firm known for its integrity, like the Starks in the original, while the Lannisters could own a powerful media conglomerate, always using underhanded tactics to stay on top.
Jon Snow could be a young journalist trying to uncover the truth about the corrupt power dynamics in the city. He's an idealist, much like in the original, and he's not afraid to take on the powerful families who control the media and politics.
One idea could be exploring what would happen if a minor character, like Gendry, had a more prominent role in the story. He could potentially become a powerful lord and change the political landscape.
A great idea for 'Game of Thrones fanfiction' is to rewrite the story from the perspective of the smallfolk. For instance, how did they really feel during all the wars and power struggles? How did the common people in King's Landing cope with the different rulers? You could also explore a fanfiction where the White Walkers are not the villains. What if there was a misunderstanding and they were actually trying to protect the realm from some other greater threat?
One idea could be exploring what would happen if Jon Snow was raised by the Starks as a trueborn son. Another could be a fanfiction about Daenerys Targaryen's journey if she had made different alliances earlier. Or perhaps a story about Arya Stark training with a different master assassin.
One idea could be exploring what would happen if a minor character like Gendry had been secretly trained in magic. He could use his newfound powers to unite the smallfolk against the warring nobles. Another plot could revolve around a female knight from the North who disguises herself as a man to fight in the wars, and along the way, she discovers secrets about the White Walkers that no one else knows. Or perhaps a fanfiction where Daenerys and Sansa form an alliance much earlier and together they reshape the power dynamics of Westeros.
In 'Game of Thrones Crossover Fanfiction', a cool concept would be crossing it with 'Alice in Wonderland'. Alice could wander into Westeros and disrupt the power balance with her strange and magical ways. Another idea is to cross it with 'The Hunger Games'. Have the districts be like the different regions of Westeros and the Capitol be King's Landing. And a crossover with 'Supernatural' where the Winchester brothers hunt down the supernatural threats in Westeros.
A cool fanfiction concept could be a situation where the magic in Game of Thrones has an impact on Smallville. Suppose a powerful sorcerer from Westeros accidentally opens a portal to Smallville. This could lead to all kinds of chaos as the residents of Smallville have to deal with magic they've never seen before. On the flip side, the Kryptonians' powers could be seen as a threat in the eyes of the Game of Thrones characters, leading to a potential conflict. Or perhaps some of the noble houses in Westeros could try to form alliances with the powerful beings in Smallville for their own political gain.
One idea could be a story where a character from 'Game of Thrones' is transported into the world of 'For Honor' and has to adapt to its combat styles. For example, Jon Snow finding himself in the middle of a battle in 'For Honor' and using his skills to survive. He might form alliances with the different factions in the game, much like he did in Westeros.
A possible idea is to have a character like Daenerys Targaryen receive visions similar to those in the Bible. These visions could guide her in her quest for the Iron Throne, but also make her question her actions and power-hungry nature. It would be an interesting take on her character development.
An interesting 'oc game of thrones fanfiction' could focus on an OC who is a female knight in a world dominated by male warriors. She could face discrimination but also prove herself in tournaments and battles. Maybe she becomes a trusted ally of a major character like Jon Snow. Or you could have an OC who is a bard that spreads tales which either inspire or deceive the people of Westeros. Also, an OC who is a foreign diplomat trying to broker peace deals between the warring factions while having their own hidden agenda would be a great concept.