We added filter for email order items arguments for shipment status email. If user want to show product image in order items use below code and put in functions.php of your theme.

ast_email_order_items_args.php

add_filter( 'ast_email_order_items_args', 'ast_email_order_items_args_callback' );

function ast_email_order_items_args_callback( $args ) {   
   $args['show_image'] = true;   
   return $args;
}