向woocommerce电子邮件添加其他详细信息

My Woocommerce site is a marketplace platform and I want to output the image of vendor's store logo (WC Vendors plugin) in the Woocommerce order emails. So when a customer receives the order email they can see the vendor store's logo in the order email. I tried the code below but not sure why the image is not being outputted. In the database, the store logo is placed under _wcv_store_icon_id.

add_action('woocommerce_email_after_order_table', '_wcv_store_icon_id', 10, 4);
function _wcv_store_icon_id( $order,  $sent_to_admin,  $plain_text,  $email ){
    foreach($order->get_items() as $item_values){
        // Get the product ID for simple products (not variable ones)
        $product_id = $item_values['product_id'];
        $vendor_shop    = urldecode( get_query_var( 'vendor_shop' ) );
        $vendor_id      = WCV_Vendors::get_vendor_id( $vendor_shop );
        $output = wp_get_attachment_image_src( get_user_meta( $vendor_id, '_wcv_store_icon_id', true ), 'full' );

    if ( is_array( $output ) ) {
        $img = $output[0];
    }
    return $img;
}