Starting from WPBakery Page Builder 4.5.0 there is an option to set Parallax effect for row background within row parameters window. If there is no parallax background image specified it will use background image from Design Options tab of the row. Parallax parameter allows choosing one of two parallax effects – simple and fade.
Tip: It is allowed to combine parallax background image (in PNG format) and Design Options image to create even more advanced overflow effects based on parallax.