removing template tags will not help performance wise (although it also works)
You should disable random image in includes/constants.php:
// If you have a lot of images in your database,
// the random image function could make your programm slow.
// Try first to set "SHOW_RANDOM_CAT_IMAGE" to 0.
define('SHOW_RANDOM_IMAGE', 1);
define('SHOW_RANDOM_CAT_IMAGE', 0);