by Kharis Sulistiyono on WordPress.org

Uploader field
Only single featured image is not enough sometimes. So you can have one more by using this plugin. It is just 7 kilobytes PHP file which adds image uploader field under post editor.
Printing the image output is very simple. Just use this code in your template file.
$id = get_post_meta($post->ID, 'iumb', true);
$image = wp_get_attachment_image_src($id, 'full-size');
echo $image;
This very first release doesn’t support custom post type. Worry not, for the next version it does.
Contact the plugin author: Kharis Sulistiyono
Are you a developer want to contribute to develop this plugin? Go to GitHub page.