mitcho (Michael Yoshitaka Erlewine)

This plugin adds a big red “preview” watermark to post previews. Never again be confused whether you’re looking at a preview or a published post!
Note: This plugin may not work well if your theme involves a background image on your <code>body</code>.
This plugin is a component of the <a href="http://ecs.mit.edu" rel="nofollow ugc">MIT Educational Collaboration Space</a> project.

Distinct Preview

This plugin adds a big red "preview" watermark to post previews. Never again be confused whether you're looking at a preview or a publi …

sverde1

This plugin allows you to watermark your uploaded images. You can create watermark with different fonts, colors and 
apply those watermarks to different image sizes (thumbnail, medium, large, fullsize). You can also position the watermark 
anywhere on the image within Watermark RELOADED settings. Watermarking settings are simple to use and provide you with 
instant preview of how your watermark will look like on the uploaded image.
<a href="http://eappz.eu/en/products/watermark-reloaded-pro/" rel="nofollow ugc">Upgrade to Watermark RELOADED Pro</a> for more 
watermarking features:
<ul>
<li>watermark opacity</li>
<li>image watermark</li>
<li>watermark background color</li>
<li>text watermark with outline</li>
<li>text watermark with variables</li>
<li>upload time option to turn off the watermarking</li>
<li>many more amazing features</li>
</ul>
Requirements:
<ul>
<li>PHP5</li>
<li>GD extension for PHP</li>
<li>FreeType Library</li>
</ul>
To-do:
<ul>
<li>Watermark RELOADED Bug fixing (request by: all)</li>
<li>Don’t display watermark on images where watermark would overflow image (request by: alex)</li>
<li>Watermark aditional image sizes added by other plugins (request by: twincascos)</li>
<li>Watermark images that were uploaded before plugin was installed (request by: anchy-9, Blogging Junction, Ashkir, Mobile Ground, Nicolas)</li>
<li>Image size aware watermark (request by: brohism)</li>
<li>Watermark outside picture</li>
</ul>

Watermark RELOADED

Add watermark to your uploaded images and customize your watermark appearance on a user friendly settings page.

Distinct Preview vs Watermark RELOADED