The Sylius Better SEO Plugin allows you to add additional SEO information to products and taxons.
Currently, the following is supported:
SEO Meta tags and image on Products and Taxons
Google Rich Snippets on Products.
The plugin provides you with an extra tab in the admin to set these SEO values. There's some fallback to default values (eg. product name as meta tag title), in case you don't fill out the details.