//Store the image names in an array
var imageNames = new Array("cat.jpg", "dog.gif", "moose.png");

//Pass the array to the function that will preload them
preloadImages(imageNames);

function preloadImages(imageNames)
{
        //Create an Array object that will hold each image's name and location
        document.imageArray = new Array;

        //Loop through the image names
        for(var i = 0; i < imageNames.length; i++)
        {
                //Create an Image object for the particular image name
                document.imageArray[i] = new Image;

                //Specify the Image object's folder location
                document.imageArray[i].src = "http://mysite.com/images" + imageNames[i];
        }
}