This functionality is part of core in later versions of WordPress. This plugin is left up only for posterity
WordPress 3.0 bundles support for custom headers in themes. If a theme supports it, a custom image can be used for a page header. Users have to choose which header image will be used.
With this plugin, instead of having to choose which header image to use, the header image is chosen at random from the list of available images. Refresh the page to see the magic work.