var img = new Array();
img[0]="random/index-1.jpg";
img[1]="random/index-2.jpg";
img[2]="random/index-3.jpg";
img[3]="random/index-4.jpg";
img[4]="random/index-5.jpg";
img[5]="random/index-6.jpg";
img[6]="random/index-7.jpg";
img[7]="random/index-8.jpg";
img[8]="random/index-9.jpg";
img[9]="random/index-10.jpg";

n = Math.floor(Math.random()*img.length);
document.write("<img src='"+img[n]+"'>");