images = new Array(2);

images[0] = "<img src='http://www.belfastbookbinding.com/Img/queens.jpg'></a>";

images[1] = "<img src='http://www.belfastbookbinding.com/Img/uuj.jpg'></a>";

index = Math.floor(Math.random() * images.length);

document.write(images[index]);