function pickImageFrom(whichGallery)
{

var gallery = new Array();
gallery[0] = new Array("1a.jpg","1b.jpg","1c.jpg","1d.jpg","1e.jpg");
gallery[1] = new Array("2a.jpg","2b.jpg","2c.jpg","2d.jpg","2e.jpg");
gallery[2] = new Array("3a.jpg","3b.jpg","3c.jpg","3d.jpg","3e.jpg");
gallery[3] = new Array("4a.jpg");
gallery[4] = new Array("5a.jpg");
gallery[5] = new Array("6a.jpg");

var idx = Math.floor(Math.random() * gallery[whichGallery].length);
document.write('<img src="images/random/' + gallery[whichGallery][idx] + '" class="subposition">');
}