function preload(arrayOfImages) {
    $(arrayOfImages).each(function(){
        $('<img/>')[0].src = this;
        // Alternatively you could use:
        // (new Image()).src = this;
    });
}

// Usage:

preload([
    '../images/banners/banner1.jpg',
	'../images/banners/banner2.jpg',
	'../images/banners/banner3.jpg',
	'../images/banners/banner4.jpg',
	'../images/banners/communicate.png',
	'../images/banners/communication-lg.png',
	'../images/banners/leadership-lg.png',
	'../images/banners/management-lg.png',
]);

function Swap(){
  var $active = $('#wrapper .active');
  var $next = ($('#wrapper .active').next().length > 0) ? $('#wrapper .active').next() : $('#wrapper div:last');
  var $last = $('#wrapper div#banner4');
  $next.fadeIn(500).addClass('active');
  $active.fadeOut(function(){
	$active.removeClass('active');
	$last.stop();
  });
}