Well, it might feature them in a beautifully decorated room. Aang could be giving Katara a special gift, perhaps something he made during their travels. They would talk about their hopes for the future, like starting a family. And they would end the night with a gentle embrace, looking forward to the days to come as husband and wife.
It could be a grand affair with elements from both their cultures. Aang being an Air Nomad, there might be floating lanterns and gentle wind chimes. Katara, from the Water Tribe, could have a beautiful ice sculpture as part of the decor. Their friends from all over the world would come to celebrate. Zuko would be there, of course, representing the Fire Nation. The ceremony would likely take place near a body of water, with Aang wearing his traditional Air Nomad robes and Katara in a stunning Water Tribe wedding dress, perhaps with blue silk and white fur accents.
One sweet scenario could be that Aang surprises Katara with a display of his airbending skills, creating beautiful patterns in the air that symbolize their love. Then they share a passionate kiss.
Aang and Katara's wedding would be a grand affair. All the four nations would come together to celebrate. Aang, in his traditional Air Nomad robes, would be waiting nervously at the altar. Katara, looking stunning in a Water Tribe inspired dress, would walk down the aisle with Sokka by her side. The ceremony would be filled with elements of both Air Nomad and Water Tribe traditions. There would be chanting of ancient Air Nomad prayers and the pouring of Water Tribe ceremonial water. Their friends, like Toph, would be there making jokes and adding a touch of humor to the otherwise solemn occasion. And as they exchange vows, the whole world would seem to hold its breath, for this was a union that symbolized hope and harmony between the nations.
It could also be that Katara was being overly critical of Aang's progress in learning new skills. Aang might feel frustrated and angry if Katara is constantly pointing out his flaws instead of being more encouraging, especially if he's already trying his best.
It could be a very tender moment. Aang, being the Avatar, might be a bit nervous as he leans in towards Katara. Katara, with her strong and caring nature, would probably be the one to give that final bit of encouragement with a soft look in her eyes. Their first kiss could be set after a great victory, when emotions are running high and they can't hold back their feelings for each other any longer.
During their wedding, there could be a display of bending. Aang might create a gentle breeze that ruffles Katara's hair and dress in a beautiful way. Katara could make a small, intricate ice sculpture as a symbol of their union. Their friends would give heartfelt speeches. Sokka might tell a funny story about how he knew they were meant to be together from the start. Toph would probably use her earthbending to create a unique seating arrangement for the guests. And at the end of the day, as the sun sets, Aang and Katara would take a flight on Appa to start their honeymoon, with the cheers of their friends and the well - wishes of the four nations following them.
It could be that the fanfiction writers wanted to explore a more complex and darker side of relationships. They might have written scenarios where Aang hates Katara due to jealousy, perhaps over her friendship with another character. This would add an interesting twist to the original relationship dynamics between them.
Well, it could be a very emotional moment. Maybe in the fanfiction, they are in a beautiful, secluded place, like a hidden cove by the sea. Aang might be a bit nervous, but his love for Katara gives him courage. Katara, on the other hand, would be full of affection and warmth towards Aang. They would probably exchange some soft words, and then share a gentle first kiss, starting this new chapter of their relationship.
Perhaps Katara falls in love with someone else. In a fanfiction scenario, she might meet a new character who she feels a stronger connection with. This new relationship could cause her to break things off with Aang, shattering his heart in the process.
In fanfiction, their married life could be filled with adventures. They might travel together to different parts of the world, using Aang's airbending skills and Katara's waterbending. They would also be involved in helping the people, just like they did before getting married. Their love would grow deeper as they face new challenges side by side.