Need tips on the layout Layout Slider WP

Hi guys , I’m totally clueless with responsive design since I’m more of a fixed width layout kind of a guy. I understand the layout slider uses layers and transparent png files.

I want to know about

> In the enfold example, the first slide is this wooden floor , and there’s a monitor, laptop , phone and text .

This wooden floor << what is the exact size or recommended size for a background in the layout slider ?

For the transparent png’s , I don’t get it. Do you need to make sure the png’s inside can be contained in a 960 width or lesser layout ?

Or to sum it up. How do I make the background images , and other images in the slides compatible with most formats ( mobile, pc, etc ) ?