div{
    height: 400px;
    width: 400px;
    background:
    url(../img/bgimage1.jpg) no-repeat left top,
    url(../img/bgimage-2.jpg) no-repeat right top,
    url(../img/bgimage-3.jpg) no-repeat left bottom,
    url(../img/bgimage-4.jpg) no-repeat right bottom;
}