Simple way to configure background content for all slides

[attakei]

What do you need?

Section controls (revealjs-section, revealjs-break and revealjs-vertical) can set data-background-image and data-background-video for background of slide.
Currently, to set background into all slides, we must write directives per vertical slides using revealjs-vertical.
ver
I want awesome way to set these options into every slides.