For this game jam, you are more than welcome to use pre-made assets, as long as they are free and public.
If the asset does not have the CC0 license, you absolutely have to give credit.
Attach a .txt file called "CREDITS" in your game zip folder, and add the credits in your description of your submitted game.
For music, Use the Youtube Audio library in Youtube Studio. In case someone makes a let's play, they can have the option to monetize their video
Please note, If you are using UPBGE/The blender game engine, there's a high chance people can extract the files and steal assets.
Look into the Range engine ( https://rangeengine.tech/ ) to publish your game. - it encrypts your game files.
If you don't want to do it and risk your biscuit, go for it!