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.

SEO_tools

Image ALT attribute is certainly significant for SEO and usability.
Increase the Google Search Visibility of your articles with BULK SEO Image
Without BULK SEO Image, you need to write manually the ALT attribute of each image, or you can use a plugin that does it for you, but it may slow down the loading speed of your page
Now, with BULK SEO Image, this light and simpe plugin, you can update all the ALT attributes at once.
Save one at a time, or save all changes with one click

Bulk SEO Image

Easily update all the ALT attribute of your images. Can add the Article Name automatically to all your images improving traffic from search engines.

Fix Gravatar Alt Text & Title Tag vs Bulk SEO Image