Toemat

This sidebar widget uses Google images to find a totally random image from the web and display it on your site. 
Give it a try! It adds a little fun and spontaneity to any site or page.
<ul>
<li>The widget can be styled with CSS.</li>
<li>Uses php cUrl to connect to Google’s API.</li>
<li>Seeds the search with the first sentence from a random MLIA quote.</li>
<li>Options for widget title, show caption, and show description.</li>
</ul>
Check it out!
By installing this plugin you are accepting all responsibility for the random images that show up 
on your site. The author is not responsible in any way for anything that happens as a result of the 
images.

Completely Random Widget

Uses Google images to find a random image from the web and display it on your site.

agnu

Header Watermark provides you with extra flexibility and control over the header image(s) for your WordPress site:
<ul>
<li>Use any image from your Media Library as a watermark for your header image(s)</li>
<li>Control the placement and opacity of the watermark</li>
<li>Select any suitable image from your Media Library as your header image(s)</li>
<li>Control which images are used for random header images</li>
</ul>
<h3>Requirements</h3>
Header Watermark requires the following to work:
<ul>
<li>GD Library PHP extension – version 2.0.28 or higher</li>
<li>The WordPress theme must use the get_header_image() function to generate the header image and must also define the HEADER_IMAGE_WIDTH and HEADER_IMAGE_HEIGHT constants</li>
</ul>
<h3>Themes</h3>
This plugin works with the Twenty Ten theme with no further configuration.
If you use this plugin with the Twenty Eleven theme, you may see a notice at the top of your website/WordPress admin pages like this:
<blockquote>
Notice: Constant HEADER_IMAGE already defined in /var/www/yoursite/wordpress/wp-content/themes/twentyeleven/functions.php on line 118
</blockquote>
You may also find that you get occasional errors on some WordPress admin pages, for example if you activate a different theme.
To prevent the notice and errors, find and change the following line in the functions.php file of the Twenty Eleven theme:
Change this: 
 define( ‘HEADER_IMAGE’, ” ); 
to this: 
 if ( ! defined( ‘HEADER_IMAGE’ ) ) { 
 define( ‘HEADER_IMAGE’, ” ); 
 }
Any other themes that define the HEADER_IMAGE constant may have the same problems and need to be altered in the same way for the plugin to work.

Header Watermark

Add a watermark image to your WordPress header image and use suitable images from your media library as the header image(s).

Completely Random Widget vs Header Watermark