Dynamically Rename Images

Is it possible to rename images dynamically? Say that I had something like image1.png, and I don't want to rename it on the server. I'm working on an image rotater for a forum that doesn't allow anything but image files as signatures. Here's my code so far: <?php //LolRotator //add images. not too hard. $images = array("image1.png", "image2.png", "image3.png"); //which one do we gets? $show = rand(0, (count($images)-1)); //i r got u picture. echo '<img src="'.$images[$show].'"/>'; ?> I used mod_rewrite, which makes it from image.php to image.png. But, because the files aren't named image.png, it doesn't work. I need to figure out somethign between lines 8 and 10 to change the file name to image.png. Is there a way to do this?