var NumBGImages = 3;
var randNum = Math.floor(Math.random() * NumBGImages);
var cor = new Array(3);

// Colocar as cores de fundo da coluna da esquerda, referentes a cada foto:
cor[0]="#FFFFFF";
cor[1]="#FFFFFF";
cor[2]="#FFFFFF";

document.write('<table width="100%" border="0" cellspacing="0" cellpadding="10" height="100%" bgcolor='+cor[randNum]+'><tr><td valign=top>');
document.write('<img src="images/software' + randNum + '.jpg" alt="" border="0">');
document.write('</td></tr></table>');