One interesting scenario could be them exploring hidden parts of Hogwarts together. They might find a secret room filled with old magic artifacts that have been long forgotten. This could lead to an adventure where they have to figure out how to use or protect these items from falling into the wrong hands.
Another scenario could be that they start a secret club at Hogwarts. A club where they teach younger students how to defend themselves against the dark arts in a more practical way than what is taught in the regular classes. This club becomes a haven for students who are worried about the return of dark forces and want to be better prepared.
In some fanfictions, they could be studying together in the library but also stealing glances and little touches. It adds a cute and romantic aspect to their relationship while still being in the Hogwarts setting. For example, Ginny might help Harry with his Potions homework, and they end up sharing a sweet moment over a difficult potion recipe.
One interesting scenario could be that they have a dinner by the lake at Hogwarts. Ginny might have prepared all of Harry's favorite foods, like treacle tart. They could be reminiscing about their adventures at Hogwarts while enjoying the meal.
Well, in some fanfictions, a great scenario is when Harry chooses 'dare' and Ginny dares him to go into the Forbidden Forest at night without his wand. As for truth, Ginny might be asked the truth about whether she ever had a crush on one of Harry's friends. Also, Harry could be dared to imitate Professor Snape's voice during a truth or dare session.
Another scenario could be them working in the field of magical creature conservation. They might team up to save an endangered species. Harry's experience with magical creatures like Buckbeak and Ginny's love for all things magical could lead them to create a sanctuary or a breeding program for the creatures.
One interesting scenario could be Ginny getting ready for the Yule Ball with the help of her friends. They might be fussing over her dress, trying different hairstyles, and giving her advice on how to act around Harry at the ball.
In some fanfictions, there might be a scenario where Harry and Ginny get engaged during a dangerous adventure. They could be on a mission to defeat a new dark wizard, and in a moment of calm before the final battle, Harry realizes that he doesn't want to face anything else without Ginny by his side, so he proposes. Or perhaps it happens during a celebration at Hogwarts. After a big victory for the school, like winning the House Cup, Harry takes Ginny to the Astronomy Tower and asks her to marry him. There could also be a situation where Ginny is the one who takes the lead. She might plan a special date and then propose to Harry, showing her strong and independent character.
In some fanfictions, it could be that they are caught by Hermione and Ron, which leads to a lot of teasing and awkward moments. For example, Ron might make a big fuss about it while Hermione tries to be more diplomatic.
In some fanfictions, the wedding might be in danger. Maybe Voldemort's remaining followers try to disrupt it. This would lead to an exciting showdown where Harry, Ginny, and their friends have to use their magic skills to protect the wedding. It could also be a chance for Harry to show how far he has come since the end of the war, using his leadership and power to keep everyone safe while still enjoying his big day.
One scenario could be that he is poisoned by a mysterious potion slipped into his food in the Great Hall. Maybe a Death Eater sympathizer among the students manages to do this.
One interesting scenario could be that the students in the Gryffindor common room gather around to read a really exciting fanfiction about Harry Potter in book 4. They might be laughing at the creative new adventures the author has written for Harry during the Triwizard Tournament.