Disclaiming Banner: I would sorely love to own ATLA, I really would. But I don't, and so Sokka is staying right where he is.
War paint
The Southern Water Tribe didn't do betrothal necklaces. Their settlements had always been smaller than the Northern Tribe's so they'd never needed to separate couples off from the masses with physical tokens. They'd never had the resources for it either. Stone and plant fiber were in shorter supply in the south. And as the Water-benders were taken by the Fire Nation raids, survival took precedent over such implications of wealth. Gifts of pelts, meats, quality building materials to make their life together safe and comfortable; that was what a man of the Southern Tribe provided to a woman and her family during courtship.
But Suki wasn't Water Tribe and the things Sokka could provide didn't have the same meaning to her. This was a problem. He couldn't even ask her own parents about it. Her father had been lost at sea during a fishing voyage and her mother had been a Kyoshi Warrior before her and died in a border skirmish with the Fire Nation. It was a really big problem; but Sokka was good at thinking new ways around problems.
When he asked Suki to marry him, Sokka presented her with Warrior's Wolf Paint.