Hi!
In the interest of giving developers as much freedom as possible for the jam, you can use whatever assets are available to you as long as they are licensed or available to the public. No need to list them out.
The theme is not at all required, just a fun addition to make the jam more cohesive.
Thank you for the post - as this is the first edition of this jam, I'm still working out some of the kinks. I'll be sure to update the main page to reflect your questions. I hope you'll participate and have fun doing so!
All the best,
CG