Have you ever wanted to change you boting gray default gravatar to something more catchy? Here is a code that implements your own avatar image. Just copy and paste it into functions.php.
add_filter( 'avatar_defaults', 'custom_avatar' );
function custom_avatar ($avatar_defaults) {
$myavatar = get_bloginfo('template_directory') . '/images/custom_avatar.gif';
$avatar_defaults[$myavatar] = "Custom Avatar";
return $avatar_defaults;
}
Don’t forget to name your new avatar image custom_avatar.gif.
Now you can go to your admin panel Settings->Discussion and change the icon of your default gravatar.