Recently MyWebsiteAdvisor,  an author of  wordpress released new plugin for wordpress.  This plugin is allows you to watermark your uploaded images using a PNG image file with transparency viewing. The plugin is designed with user friendly to settings page that allows easy for control over the appearance of your watermark. And you can also set your watermarks to by specific percentage of image you want to watermark. With Watermark view, the images in your site will more beautiful looks.

To use watermark plugin required PHP 5, GD extension for PHP, and you have to change the default location of watermark, and also you have to turn off watermark when uploading an image. For more information and download visit the http://MyWebsiteAdvisor.com/tools/wordpress-plugins/transparent-image-watermark/. For how to you may see the video below.
[youtube http://www.youtube.com/watch?v=fEhZK1U8W94&hl=en_US&feature=player_embedded&version=3]