Thank you. The images in the demo fill the screen as long as you are using a lower resolution monitor. On a 1920px resolution monitor, there is a 60px gap on each side. Below is the styling from Version 1.1.2. I plan to just uncomment the background-size property. Just pointing out the issue in case fixes are being pushed out.
.front-page-1,
.front-page-4,
.front-page-5,
.front-page-7,
.front-page-9,
.front-page-12 {
/*background-attachment: fixed;*/
background-position: 50% 0;
background-repeat: no-repeat;
/*-webkit-background-size: cover;
-moz-background-size: cover;
background-size: cover;*/
}