One cool storyline could be that Spiderman discovers a new type of webbing while on a joint mission with Young Justice. This webbing has some sort of special property, like being able to disrupt magic or technology. And the whole story could revolve around him and the team trying to figure out how to use this new webbing to their advantage and also keep it out of the hands of the villains.
Perhaps a storyline where Spiderman teams up with a Young Justice member who has similar powers to one of his foes in his own universe. They could share their experiences and strategies on dealing with such powers. For example, if there was a Young Justice member with powers similar to Electro, Spiderman could give tips on how to counteract electricity - based attacks.
A third interesting storyline might involve a secret alliance between a member of the Justice League and a villain that the Young Justice team discovers. This discovery then sets off a chain of events where the Young Justice team has to decide whether to trust the rest of the Justice League and how to handle this new information without causing a complete breakdown in the superhero community.
One possible storyline could be the team celebrating a successful mission with a fireworks display. The characters could have personal moments during this time, like Robin reflecting on his growth as a hero. Another could be a villain using fireworks as a distraction for a heist, and the Young Justice team has to stop them while also dealing with the chaos of the fireworks.
One interesting storyline could be about a character developing claws as a new power and struggling to control it. For example, they might accidentally harm their friends during training sessions. Another could be a mystery where the origin of the claws is related to an ancient artifact in the Young Justice universe. And there could also be a story where a character with claws has to prove themselves to the team, facing discrimination from some members who fear their power.
One interesting storyline could be a young hero who discovers their powers while being part of the circus in the Young Justice universe. They might have to hide their abilities at first for fear of being different. Another could be a mystery involving the circus performers where they seem to be disappearing one by one, and the Young Justice team has to figure out what's going on. A third storyline could be about a circus act that is actually a front for a secret training ground for new superheroes.
Well, in some Young Justice Heroes fanfiction, there are storylines focused on the relationships between the characters. Like a love triangle between Robin, Aqualad, and Artemis. Or a story that delves into the family dynamics of the heroes, such as how Wally West's family copes with his superhero life. There could also be a story about a new hero emerging within the Young Justice team and how they are trained and integrated into the group.
Some fanfictions play with the idea of power - swapping. Maybe a young hero from Young Justice gets the powers of a Justice League member and vice versa. It's a really cool concept as it forces the characters to adapt to new abilities and challenges, and it often leads to some really fun and unexpected storylines.
A great fanfiction idea could be that Artemis and Superboy are stranded on an alien planet. Superboy has to deal with the unfamiliar environment while Artemis tries to find a way to signal for help. Along the way, they discover secrets about each other's pasts that they never knew before, which deepens their relationship.
One popular storyline could be them teaming up for a dangerous undercover mission. They have to rely on each other's skills, with Tigress' combat expertise and Nightwing's strategic mind. Another might be a story where Nightwing has to rescue Tigress from a powerful enemy who has captured her. This could lead to a deepening of their relationship as they face the aftermath together. There could also be a storyline about their past interactions and how they first came to trust each other.
Another storyline could involve a crossover where Static gets transported to the Young Justice universe. He has to adapt to their way of doing things while also helping them solve a mystery that has been plaguing their world. Maybe it's a new type of villain that uses technology in a way they've never seen before.
One interesting storyline could be Starfire's unique powers interacting with the Young Justice team's abilities. For example, her starbolts might combine with Superboy's strength in a new way during a battle. Another could be her learning about Earth's culture from the Young Justice members, leading to some comical misunderstandings.