The traditional Mexican holiday of Day of the Dead i.e. Día de los Muertos

While the holiday's observances include spending time in cemeteries, making shrines to the dead, and displaying artistic representations of skulls and skeletons, the occasion is festive, rather than morbid. Death isn't seen as the end of one's life, but as a natural part of the life cycle; the dead continue to exist much as they did in their lives, and come back to visit the living every year.

So it is mostly about celebrating life and representing skulls and skeletons. It gets bigger and bigger every year, so if you want to know more about it, then please check this link for example.