Combining text in an array in JavaScript
perhaps you can try apply(), then you can pass in the image paths as an array:

preLoadIamges.apply(this, absoluteFileNames)


then you can build you array in a the way you like, perhaps looking at this unobtrusive implementation of Array.map:

var directory = "/media/img/elements/frontpage/"
var fileNames = ["1.jpg","...","9.jpg"]; 
var absoluteFileNames = fileNames.map(function (value) { 
    return directory + value; 
});