I've created these royalty free backgrounds in Medibang Paint. Feel free to use these backgrounds in your own (non-commercial) projects. Please tag me or share a link to your finished projects so that I can see what you have created.

The Simpsons animation background:

https://art.ngfiles.com/images/1323000/1323277_aperturejam_the-simpsons-animation-background.png?f1592902076

African Savannah animation background:

https://art.ngfiles.com/images/528000/528851_aperturejam_african-savannah.png?f1592901731