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.

Sibin Grasic

Letter Avatars enables custom avatars for users without gravatar. Avatar will be replaced with the first letter of username or e-mail.
Letter Avatars does not use any images, scripts, or font-icons. All letters will be rendered by your theme font (or Optionally via a Google font).
Features
<ul>
<li>Works anywhere – Plugin hooks into pre_get_avatar function, so the avatar size is preserved</li>
<li>Highly customizable – You can change colors, letter font, as well as the font size</li>
<li>Stylish – You can change the background and letter colors or you can randomize them for all the avatars</li>
<li>Lightweight – Plugin does not use any external stylesheet, image, or js files. It only adds a small inline css in your header</li>
<li>Highly compatible – You don’t have to edit your theme / plugin files, it works automatically and plays nice with other plugins</li>
<li>Works with BuddyPress – Users and groups without gravatar / local avatar will use Letter Avatars</li>
<li>Works with YITH Reviews for WooCommerce – Avatars in reviews support Letter Avatars</li>
<li>Works with WP User Avatar – Users with Custom Avatar will use those, users without avatar will default to Letter Avatar</li>
</ul>

Letter Avatars

Nice

Nice work! Much better than "Mystery Man" for unknown users.



Featured on iThemes Training Plugin Roundup, March 2016

I chose this plugin over another similar plugin which had more installs and reviews because this plugin offers a solution as simply as possible. No images or scripts needed, just plain old CSS for the win. Kudos to the developer.

Lightweight & Elegant Solution

Works great and with good support by the maintainer. Thanks for your work!

Works great and good support

Sets custom avatars for users without gravatar. Avatars will be replaced by first letter of usename (or e-mail) on a colorful background

Author Grid vs Letter Avatars