I know that the rules state that all work has to be done within the time frame of the jam, but would I be able to use CC art assets even though the ones I have in mind were created beforehand?

When you say CC art assets are you referring to Creative Commons...?

Yes, that's what I meant. c:

Yeah you can use things in the public domain and creative commons as long as you reference them in a sort of credit section where possible.

Awesome, thank you!