Sounds like you need javascript..... moving to the Clientside Technology forum.
I believe a function would look something like this:
function rotateImage(img) {
var newsrc="";
IO = document.getElementById(img);
switch(IO.src) {
case "image1.jpg":
newsrc="image2.jpg";
break;
case "image2.jpg":
newsrc="image1.jpg";
break;
}
IO.src=newsrc;
}
window.onload= function () {
setTimeout('rotateImage("rtIMG")', 5000);
}
And the HTML:
<img id="rtIMG" src="image1.jpg" />
Hope that helps some.