var randnum = Math.random(); 
var inum = 10; 
// Change this number to the number of images you are using. 
var rand1 = Math.round(randnum * (inum-1)) + 1; 
images = new Array 
images[1] = "images/headers1.jpg"
images[2] = "images/headers2.jpg"
images[3] = "images/headers3.jpg"
images[4] = "images/headers4.jpg"
images[5] = "images/headers5.jpg"
images[6] = "images/headers6.jpg"
images[7] = "images/headers7.jpg"
images[8] = "images/headers8.jpg"
images[9] = "images/headers9.jpg"
images[10] = "images/headers10.jpg"
// Ensure you have an array item for every image you are using. 
var image = images[rand1]