Using layout to set a full page background image (responsive & displaying entire image)

Currently I’m trying to get a somewhat odd image to display full screen using the layout, but traditional CSS just doesn’t display anything, just a white background. On other pages I can set it on each, thought it’s still a little funky, but it just doesn’t seem to work here.

GDrive link to image: Layout_3.webp - Google Drive

background: url(Layout_3.webp) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;

My goal is to have the border visible on all sides, while allowing the page to be responsive. Any help? Further specifics I can offer?

Any ideas? The goal is just not to repeat this image on every page.

Update! Had the wrong set prop! However, now the image is extending vertically infinitely…