window.onload = choosePic;

var myPix = new Array("../../../../_images/subheader/sh001.jpg", "../../../../_images/subheader/sh002.jpg",
    "../../../../_images/subheader/sh003.jpg", "../../../../_images/subheader/sh004.jpg",
    "../../../../_images/subheader/sh007.jpg", "../../../../_images/subheader/sh009.jpg",
    "../../../../_images/subheader/Bar.jpg", "../../../../_images/subheader/snap_crack.jpg",
    "../../../../_images/subheader/wing-ah.jpg");

function choosePic() {
    randomNum = Math.floor((Math.random() * myPix.length));
    document.getElementById("myPicture").src = myPix[randomNum];
}