How can I get thumbnails and links to related products to display on pages?

I would like to be able to display images of (and links to) related products automatically on product pages, either by adding a widget or through shortcode.

As far as I can tell, none of the widgets available under Appearance > Widgets make this possible, nor do any of the shortcodes.

Am I missing something obvious or is there another method I need to employ to achieve this?