// pick a number between 1 and 12
  var num = Math.floor(Math.random()*12) + 1;
  
  // give me a prepended zero if we're below 10 on the number.
	var numstr = "";
	if (num < 10)
	{
	  numstr = "0" + num;
	}
	
	// build the image name
	var imgName = "tv" + numstr + ".jpg";
	
	// set the image source
	document.getElementById('tvimg').src = "images/" + imgName;