Using image.php to call every subcat and cat icons from the db can be very costly. Remember the browser won't cache any of the image data coming from the database, so if your using such code on the main cat or subcat, you will notice a somewhat larger load on the server. The best method for this is to remove the category icons from using the database and using the file system so they are cached within the browser.
anyhow, just a tip.
