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.

Patrick Chia

This plugin allows you to generate a <code>gravatar favicon</code> for your blog and admin logo included Apple touch icon. Just activate the plugin, and it will add gravatars to your blog template and admin panel automatically, no setting and nothing. But you must enable your avatar(Discussion Settings). (W6A4N4-L26P6-WSH)

Gravatar Favicon

This plugin allows you to generate a gravatar favicon for your blog and admin logo included Apple touch icon.

Author Grid vs Gravatar Favicon