mdiamondstone

authorGrid is a sidebar widget that displays the avatar of any author on your blog with at least one published post in grid form. You 
can set how large the avatar should be, how many columns (or rows) you’d like in the grid, and the display title of the widget.

Author Grid

Sidebar widget that displays the avatar of all of the authors on your blog in grid form.

Dev49.net

DanielAGW

BuddyPress First Letter Avatar sets custom avatars for users without profile picture or Gravatar. The avatar will be a first letter of user’s name. You can also configure plugin to use any other letter to set custom avatar.
BuddyPress First Letter Avatar is based on my other plugin – <a href="https://wordpress.org/plugins/wp-first-letter-avatar/" rel="ugc">WP First Letter Avatar</a>. BuddyPress First Letter Avatar is basically the same thing, but programmed to work with BuddyPress.
BuddyPress First Letter Avatar includes a set of beautiful, colorful letter avatars in many sizes. Optimal size will be chosen by the plugin in order to display high quality avatar and not download, for example, big 512px avatars when only 48px is needed… PSD template for avatar is also included.
You can also create your own avatar set by creating new directory next to ‘default’ folder and following the naming convention from ‘default’.
By default, custom avatar will be set only to users without profile pictures and Gravatars, but you can change that in settings and not use Gravatar/profile pictures at all.
BuddyPress First Letter Avatar helps you bring more colors into your BuddyPress site. Plus, your users will be more willing to actively participate in your site since they can actually relate to these avatars much better than to the Mystery Person.
All images were compressed using the fantastic <a href="https://tinypng.com/" rel="nofollow ugc">TinyPNG</a>, so avatars are incredibly light and ultra-high quality.
Plugin is also available <a href="https://github.com/Dev49net/buddypress-first-letter-avatar" rel="nofollow ugc">on GitHub</a>.
<h4>Requirements</h4>
BuddyPress First Letter Avatar requires at least PHP 5.4. It does not work properly on PHP 5.3.x and earlier.

BuddyPress First Letter Avatar

A WordPress-BuddyPress plugin to set fancy custom avatars for users with no Gravatar and no profile picture.

Author Grid vs BuddyPress First Letter Avatar