// fill the array imagenames from PHP
// by scanning the filenames in the directory.
// Have a look at: http://nl2.php.net/manual/en/function.readdir.php
// for some examplecode

var imagenames = ["contact3.png", "kontaktkom.png"];
var baseImageURL = "";
var imgcount = -1;
var nrOfImages = imagenames.length -1;

function nextImage(){
imgcount++;
if(imgcount > nrOfImages) {
imgcount = 0;
}
// make full URL to image
var newImageSrc = baseImageURL + imagenames[imgcount];
// set the new Image
document.images.myImage.src=newImageSrc;
// Come back here in 5 seconds
setTimeout("nextImage()" , 5000);
}