TrueFalse

Plugin automatically fills the ALT attribute in HTML IMG tag on every insert a new image into the post, if it is not full.
Note 1. “AFI” does not attribute alt attribute to the images added to the media library.
Note 2. On the role of ALT attribute for the search engines read here:
<ul>
<li>http://help.yandex.com/images/?id=1112581</li>
<li>http://support.google.com/webmasters/bin/answer.py?hl=en&answer=114016</li>
</ul>

ALT for images

Automatic insertion of alt attribute header-based embedded image.

negi.ga.suki

This plugin will add the HTML code to the submit button portion of the comment. 
You will be able to display messages and images there. The operation is very easy.

ALT for images vs SAMURAI