var ChangeImages =
{
    init: function () 
    {
        var images = $(".imagesListImage");

        for (var i = 0, ii = images.length; i < ii; i++)
        {
            $(images[i]).bind("click", ChangeImages.clickListener);
        }
    },

    clickListener: function(event)
    {
        var img = this.childNodes[0];
        var imgSrc = img.src;
        var newImgSrc = imgSrc.replace("s=2", "s=3");

        var mainImage = $(".mainImage")[0];
        mainImage.src = newImgSrc;
        mainImage.alt = img.alt;

        event.preventDefault();
    }

}

ChangeImages.init();