If I have a div that contains images and text, is it possible to use this div\'s content as a background for, let\'s say, a section ?<
Use the CSS element() function. See https://developer.mozilla.org/en-US/docs/Web/CSS/element. Currently available only in FF under the -moz-element prefix. Example:
An alternative would be to play with SVG's foreignObject tag, cloning the HTML for the element you want to use as background into it.
Spec is at http://dev.w3.org/csswg/css-images/#element-notation.