He might focus on rebuilding Hogwarts. After all the destruction, it would be a huge task and he could use his influence and skills to bring it back to its former glory.
In many fanfics, Harry Potter might become an Auror after Hogwarts, using his skills to fight dark magic. He could also start a family with Ginny and raise their children in a world that's gradually recovering from the war.
In the 'harry potter after hogwarts fanfic', a really interesting plot could be about the discovery of new magical creatures or lost spells. Harry, being the adventurous type, might go on quests to explore these new elements. He could also get involved in international wizarding relations, using his fame and experience to bridge gaps between different wizarding communities around the world. This would open up a whole new world of magic for the readers to explore.
Obviously, Harry Potter himself would be a central character. Ron and Hermione, his closest friends, would also likely be in it. Ginny, as Harry's love interest, would probably play a significant role too. Other characters like Neville, who has grown into a strong wizard, could also be featured. And of course, we might see some of the old Hogwarts professors, perhaps McGonagall still guiding the school in some way.
A great plotline in these fanfics can be the integration of new magical creatures into the post - battle Hogwarts. With the upheaval of the battle, magical barriers might have weakened, allowing new creatures to enter. The students and teachers then have to figure out how to co - exist with them. There could also be a story about the Muggle - born students trying to bridge the gap between the wizarding world and the Muggle world more than ever, as they've seen the destruction that secrecy can bring.
Once, in the Harry Potter Hogwarts Battle Game, a strange glitch occurred. As the players were battling a horde of Death Eaters, suddenly the game's graphics distorted. The walls of Hogwarts started to ooze a black, slime - like substance. The characters' spells backfired, and instead of hitting the enemies, they were hitting their own team. One by one, the avatars of the players started to disappear into the darkness, leaving only their screams echoing in the virtual halls of Hogwarts.
Harry Potter is often still a main character. He might be involved in the rebuilding efforts or mentoring the younger students. Hermione Granger could also be there, using her vast knowledge to help solve post - battle problems. Ron Weasley as well, perhaps starting a new business in Hogsmeade.
Draco Malfoy is often a popular character in these fanfictions. After Hogwarts, he might be trying to redeem himself, or there could be a love story between him and a character like Hermione. His complex past and family history make for interesting storylines. Another popular character could be Neville Longbottom. He has grown so much during his time at Hogwarts, and in fanfiction, he could be a great teacher at Hogwarts, passing on his knowledge of Herbology and his courage to the new students.
In the fanfic, Harry Potter could meet the new generation of students. They would be in awe of him. He might also encounter some of the ghosts, like Nearly Headless Nick, who would surely have some interesting stories to share since Harry left. And there's a good chance he'll meet the caretaker, who would probably give him a hard time about coming back and causing a stir. Moreover, he could cross paths with some of the older students who idolize him and want to learn from his experiences.