depending on which Spanish-speaking country you live in, one major party that's celebrated is Dia de Los Muertos. to decorate you would want to make a lot of sugar skulls and bright colored streamers and other things. the custom of this celebration is to celebrate the dead, once the party as started there is almost always a parade to be held in the streets of the country where many people are dressed up with brightly colored skulls painted on their face. the parade last from anywhere between a few hours or it goes all the way to sun down.
not sure what else to put but i hope helps in some way, if not i apologize