Comment changer le logo de la zone admin de wordpress :
function childtheme_custom_login() {
echo '<link href="'.get_bloginfo('stylesheet_directory').'customlogin.css" rel="stylesheet" type="text/css" />';
}
add_action('login_head', 'childtheme_custom_login');
Source : codex.wordpress.org/Plugin_API/Action_Reference/login_head