var libImagesArray = new Array();
libImagesArray[0] = 'images/lib01.jpg';
libImagesArray[1] = 'images/lib02.jpg';
libImagesArray[2] = 'images/lib03.jpg';
libImagesArray[3] = 'images/lib04.jpg';
libImagesArray[4] = 'images/lib05.jpg';
function newImage() {
document.getElementById("libImage").setAttribute("src",  libImagesArray[Math.round(Math.random()*4)])
}