var images = new Array();

images[0] = "rotation/house06a.jpg"; 
images[1] = "rotation/house06a.jpg";
images[2] = "rotation/house06a.jpg";
images[3] = "rotation/house06a.jpg";
images[4] = "rotation/house06a.jpg";
images[5] = "rotation/house06a.jpg";

function ShowImg() {
var number = images.length;
var increment = Math.floor(Math.random() * number);
var strTemp ='<img src="' + images[increment] + '">';
document.write(strTemp);
}