I have used this in the past:
(remember not to put a comma after the last image in the array)
$(document).ready(function(){
preload([
'path/to/images/group_0.png',
'path/to/images/group_1.png',
'path/to/images/group_2.png',
'path/to/images/group_3.png'
]);
});
function preload(arrayOfImages) {
$(arrayOfImages).each(function(){
$('<img/>')[0].src = this;
});
}
(remember not to put a comma after the last image in the array)