Background image on portfolio item in boxed layout

Hi there,

I’m using WP-Backgrounds Lite plugin to set individual backgrounds for pages. The plugin works for posts as well, but the option to choose a background image doesn’t show up on portfolio items. I’ve solved this by using this for every single portfolio item:
.postid-3301 { background-image: url(“http://sgtest.jacobsenweb.dk/wp-content/uploads/2015/10/sg-background-bilbao1.jpg”);
background-repeat:round;
background-attachment:fixed;
}

Do you know how I can get WP-Backgrounds Lite to work on portfolio items? And if not, is there another plugin I can use that works with Enfold (or a workaround in Enfold without plugin?

Link to website portfolio: http://sgtest.jacobsenweb.dk/portfolio-item/am-falschen-ort-2004-2005/

Best regards