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 …

marekki

Marekkis Watermark-Plugin for WordPress can watermark your pictures an two different ways:
<ul>
<li>Insert your watermark while the picture is being uploaded.</li>
</ul>
After the activation every picture that you will upload with wordpress build-in media-uploader will be watermarked.
In the configuration-screen you can set up the position and the type of your watermark. It can be your logo (.png-file) with transparent background or a free text with color, font, size, shadow and transparency-level of your choice. See screenshots.
<ul>
<li>Insert your watermark on all chosen pictures from a directory on your web-server.</li>
</ul>
Marekkis Watermark makes possible to create a watermark on mediafiles that are already uploaded on your server. So you can mark all your old pictures with the new watermark.

Distinct Preview vs Marekkis Watermark-Plugin