Layered background image or wallpaper

Hi, quick question: instead of having a normal wallpaper or background image that scrolls at the same rate as the page, is it possible to have one that scrolls slower, as if it were layered and further back. I’ve seen it on a few wordpress sites and wondered if it’s possible to do with Enfold. If not, maybe a future feature request?

Ideally, something that also supports a slight transparency on the normal content so you can partially see through the content to the background image. A bit like the “glassy” header, but for the entire page.

Thanks