Hi there,
If your home page is a static page, you can use Simple CSS: https://wordpress.org/plugins/simple-css/
It adds a meta box when adding your page where you can add CSS for that page only.
Then you would do this:
.separate-containers .inside-article,
.one-container .site-content {
background-image: url( 'URL TO IMAGE' );
}
If your home page is your blog, you would do this:
.home .separate-containers .inside-article,
.home .one-container .site-content {
background-image: url( 'URL TO IMAGE' );
}