Newt Labs

This simple, lightweight plugin solves one particular issue. WordPress doesn’t include any alt text or a title tag when using Gravatars. This addresses that by using the comment author name for each of your comment’s Gravatars, and for any other Gravatar usage it should use the authors display name.
So if you create a post it will use your name for your Gravatars Alt text and Title tag and then for the comments it will use the commenters name for their Gravatars Alt text and Title tags.
With this plugin you can squash those pesky warnings given by SEO reporting tools that look for missing alt text and title tags.
<h3>Important Notes</h3>

Fix Gravatar Alt Text & Title Tag

Applies comment author name to Gravatar's Alt and Title tags in comments and author display name to Gravatars site-wide.

mylo2h2s

DP ALTerminator adds missing or empty ALT tags to your content images.
Thanks to various shortcodes such as <code>%%DP_TITLE%%</code> or <code>%%DP_DATE%%</code> it’s pattern can be easily customized (you can mix plain text elements with shortcodes to create complex patterns)
DP ALTerminator works when ALT tags are missing or when they are empty. Sometimes WordPress itself, visual editors, and so on, leave an ugly <code>alt=""</code> which is useless and not always recognized by other famous ALT tag managers.
DP ALTerminator works only with content images ($content variable), because I didn’t want to alter “extra” images, like widgets, logos, menu icons and so on (most of the times, you want to manually edit their ALT or leave it empty)

DP ALTerminator – Missing ALT manager

Adds ALT tags to your content images when they're missing or empty. It's pattern can be customized with simple shortcodes.

Fix Gravatar Alt Text & Title Tag vs DP ALTerminator – Missing ALT manager