img.bg {
    min-height: 100%;
    min-width: 1024px;
    width: 100%;
    height: auto;
    position: fixed;
    top: 0;
    left: 0;
}

@media screen and (max-width: 1024px){
    img.bg {
    left: 50%;
    margin-left: -512px; }
}