body, html {

 height: 100%;

 margin: 0;

}

​

#background {

background: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)), url('https://loremflickr.com/320/240');

height: 100%;

background-position: center;

background-repeat: no-repeat;

background-size: cover;

}