iframe {
    position: fixed;
    right: 0;
    bottom: 0;
    min-width: 100%;
    min-height: 100%;
    width: auto;
    height: auto;
    z-index: -100;
    background: url('/assets/images/polina.jpg') no-repeat;
    background-size: cover;
}

body{
    background-image: url(../img/chemin.png);
}