Quick N Dirty Parallax

gistfile1.js

function watch_header () {
		TweenMax.set('.fixed-header-img-obj', { y: ScrollTop/2, z:0.1 });
}
TweenMax.ticker.addEventListener( 'tick', function () {
    watch_header();
});

gistfile2.css

.fixed-header-image-obj-wrap {
	width: 100%;
	height: 100%;
	position: absolute;
	top: 0;
	left: 0;
	overflow: hidden;
}
img.fixed-header-img-obj {
	position: absolute;
	min-width: 100%;
	min-height: 100%;
	max-width: none;
	width: auto;
	-webkit-transform: translate3d(0,0,0);
	-moz-transform: translate3d(0,0,0);
	-ms-transform: translate3d(0,0,0);
	-o-transform: translate3d(0,0,0);
	transform: translate3d(0,0,0);
} 

gistfile3.html

<div class="fixed-header-image-obj-wrap"><img src="" alt="" class="fixed-header-img-obj"></div>