This plugin let’s you place notes on images like you know it from flickr. Via a additional box in the admin’s post edit view you’re able to place notes on images associated to the post.
Please take note that it’s currently no final release, so there might be bugs.
If you have any problem please consult the <a href="http://support.knuspercode.de/index.php/categories/2/knspr-imgnote" rel="nofollow ugc">support forums</a>
Uses the <a href="http://odyniec.net/projects/imgareaselect/" rel="nofollow ugc">imgAreaSelect jQuery plugin</a> by Michal Wojciechowski and is based on the <a href="http://www.sanisoft.com/blog/2008/05/26/img-notes-jquery-plugin/" rel="nofollow ugc">imgnotes jQuery plugin</a> by Dr. Tarique Sani.
<h3>Workflow</h3>
<ol>
<li>Add a new post or edit an existing one</li>
<li>Upload the images via the WordPress media upload tools and insert it in the post</li>
<li>If the post is new, safe it as draft and reload the page, the images should be visible in the thumbnail list</li>
<li>If the post is an existing one just hit the “Reload” link in the thumbnail list and the new images should be visible</li>
<li>Click the thumbnail of the image you want to add notes to and click the “add note”-Button.</li>
<li>Add all your notes, they will be automatically saved as you click “Save note”.</li>
</ol>

knspr-imgnote

This plugin let's you place notes on images like you know it from flickr.

durgathakur

This plugin allows you to add 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. Integration with JQuery Image Annotation from Chris (http://www.flipbit.co.uk/jquery-image-annotation.html) with PHP support from GitHub (http://github.com/stas/jquery-image-annotate-php-fork).
Some features:
<ul>
<li>Admin page</li>
<li>Option to approve, edit amd remove image notes in admin page.</li>
<li>Auto insert unique id attribute for all the images for image note.</li>
<li>Show notes on other pages such as home and archive.</li>
<li>Gravatar in the notes</li>
<li>Option to sync with wordpress comments.</li>
<li>Option to show thumbnail in comment list.</li>
<li>Option to include post id in every auto insert images id.</li>
<li>‘Mouseover to load notes’ on top of every image note (editable).</li>
<li>‘Link’ on top of every image note if hyperlink image (editable).</li>
</ul>

wp image annotation

Allows you to add textual annotations to images by select a region of the image and then attach a textual description.

knspr-imgnote vs wp image annotation