Makoto

This plugin allows you and your visitors to add comment as textual annotations to images by select a region of the image and then attach a textual description, the concept of annotating images with user comments. 
The text is intergrated with WordPress comment system. 
Integration with <a href="http://www.flipbit.co.uk/jquery-image-annotation.html" rel="nofollow ugc">JQuery Image Annotation from Chris</a> with <a href="http://github.com/stas/jquery-image-annotate-php-fork" rel="nofollow ugc">PHP support from GitHub</a>. 
Modified from <a href="http://www.superwhite.cc/demon/image-annotation-plugin" rel="nofollow ugc">Demon Image Annotation version 1.0</a>. 
Icons from <a href="http://www.famfamfam.com/lab/icons/silk/" rel="nofollow ugc">Fam Fam Fam</a>
Features:
<ol>
<li>Ability to add notes to your uploaded pictures.</li>
<li>Show notes on single page, front page, archive page and etc.</li>
<li>Notes synced with WordPress commenting system but there’s option to turn it off.</li>
<li>Gravatar in the notes.</li>
<li>Commentator’s name in the notes.</li>
<li>Image thumbnail appear at comment area, but there’s option to turn it off.</li>
<li>No hard coding required.</li>
<li>Admin page.</li>
<li>Remove all database if you wish to not using the plugin anymore.</li>
</ol>

Guan Image Notes

Image tagging system sync with WordPress comment system. Or also known as image notes, or image annotation.

shawfactor

LH Dashboard Notes allow you to insert noes on your wp-admin dashboard for your users using the post editor interface. If this plugin is network activated the insertion and editing of these dashboard notes is centralised on the main site of your multisite install. Allowing you to set Dashboard notes that are viewed throughout your multisite network.

LH Dashboard Notes

Allows you to create and edit notes that appear on the admin dashboard

Guan Image Notes vs LH Dashboard Notes