Putting featured image as background image

Hello, I'd like to add the featured image for each of my pages to work as a background image. For example, I'd like to have the default image in my home page (http://analymark.com/) and another image such as this one (http://analymark.com/wp-content/uploads/2015/07/147.jpeg) on this page: http://analymark.com/index.php/analyse-ergonomique-ux/ Is there a way to do this? Thanks.