The Day of the Dead, Día de Muertos, is a holiday primarily celebrated in Mexico that honors and remembers those that have died.
Often, game jams are about mechanics, themes, restrictions. The challenge in this jam is about having the courage to get personal, and through the act of creation, attempting to get closer to something real and meaningful.
This is a very different kind of jam and you may not know how to even begin. My advice is to focus on story telling, which in games is often delivered through dialogue or a big block of text at the beginning that explains what is going on. Another thing to remember is that the game does not have to be about death.