myLine = 2;
myMes = new Array(
'<img src="http://www.union-trd.com/img/JoeyJackson-image01.jpg" alt="" title="" />',
'<img src="http://www.union-trd.com/img/JoeyJackson-image02.jpg" alt="" title="" />'
);
myRnd = Math.floor(Math.random()*myLine);
document.write(myMes[myRnd]);