Jazz music has its very own characteristic, style and culture. It doesn't only live through its music, but the stories when you use the directors using the music for the right feeling. These are dramas, romances and more.
As you can imagine, there's no theme to follow. Use a topic that you want, a story (or no story). Try to adapt your jazz-feeling on a game.
To submit your game, just create and upload your finished game to itch.io from your Dashboard, and then it will be visible to choose as your submission for this game jam when you click the Submit button at the top of this page.