Customer reviews in WooCommerce include avatars of customers. In many cases, customers do not have any avatars and WordPress shows placeholders instead of avatars. If you do not want to display avatars, it is possible to turn them off in WordPress settings.
Avatars is the standard WordPress features. To configure avatars, please go to the standard WordPress settings (Settings > Discussion) and scroll to the Avatars section. Here, you can enable or disable avatars as well as configure other options.
Also, there are many third-party plugins that extend and modify the standard WordPress avatars functionality (try searching the official plugins directory). Such plugins should be generally compatible with WooCommerce reviews.