WordPress Hack To Set A Custom Default Avatar

Create a new custom Avatar. It should be 60px*60px PNG format.
Name it custom-avatar.png.
Upload this avatar image in your /wp-content/themes/yourtheme/images directory
Open you theme’s functions.php file
Copy the following given code and paste it in your functions.php file:

if ( !function_exists(‘custom_gravatars’) ) {
function custom_gravatars( $avatar_defaults ) {
$myavatar = get_template_directory_uri() . ‘/images/custom-avatar.png’;
$avatar_defaults[$myavatar] = ‘people’;
return $avatar_defaults;
}
add_filter( ‘avatar_defaults’, ‘custom_gravatars’ );
}