CSS background

Markups

#wrap {
    background: no-repeat center fixed #fff;
    background-size: cover;
}
@media only screen and (max-width: 767px) {
    #wrap { background-image: url(small.jpg); }
}
@media only screen and (min-width: 768px) {
    #wrap { background-image: url(medium.jpg); }
}
@media only screen and (min-width: 1280px) {
    #wrap { background-image: url(large.jpg); }
}

Feature