You can remove the background image from the footer widgets area.
In WordPress, go to Appearance > Customize > Additional CSS.
To change the background image, add this CSS.
Replace "images/footer-widgets-bkg.png" with the complete URL from an image in your Media > Library.
.footer-widgets { background-image: url(images/footer-widgets-bkg.png); }
To remove the background image, add this CSS.
.footer-widgets { background-image: none; }