function init()
{
	var thumbnails = document.getElementById('thumbnails').getElementsByTagName('img');
	
	for(var i=0; i< thumbnails.length; i++)
	{
		var location = thumbnails[i].src;
		thumbnails[i].onclick = function (){
				changeBackground(this.src);
			}
	}
}

function changeBackground(filename)
{
	var viewer = document.getElementById('background_example');
	viewer.style.backgroundImage = 'url('+filename+')';
}

window.onload = init;