function getRandImage(imagesArray) {
	var randIndex = Math.floor(Math.random()*(imagesArray.length));
	var randImage = imagesArray[randIndex];

	return randImage;
}

function updateImage(imagesArray) {
  	var randImage = getRandImage(imagesArray);
	var imageDir = "images/index_images/";
	var randImageStr = "<img src=\"" + imageDir + randImage + "\" alt=\"Random TZ image " + randImage + "\" />";
	var randImageDiv = document.getElementById('randImage');
	randImageDiv.innerHTML=randImageStr;	
}