You have the capability to include multiple images in a background using CSS3 http://caniuse.com/#feat=multibackgrounds
http://jsfiddle.net/79TyM/
#container {
width:200px;
height:200px;
background:
url(http://placekitten.com/100/100) left top no-repeat,
url(http://placekitten.com/g/100/100) right top no-repeat,
url(http://placekitten.com/g/100/100) left bottom no-repeat,
url(http://placekitten.com/100/100) right bottom no-repeat;
}
Originally, the requester desired the backgrounds to be stacked rather than arranged in a square. An updated fiddle can be seen here: http://jsfiddle.net/79TyM/1/
#container {
width:100px;
height:400px;
background:
url(http://placekitten.com/100/100) left top no-repeat,
url(http://placekitten.com/g/100/100) left 100px no-repeat,
url(http://placekitten.com/g/100/100) left 200px no-repeat,
url(http://placekitten.com/100/100) left 300px no-repeat;
}