This plugin provides a simple way to set an automatically scaled full screen background image.
Full screen background slideshow in any page/post, with images from WP Media Gallery, NextGEN Gallery, Flickr, Picasa, Smugmug, folder, or XML file
Create a full-screen popup without a developer. Promote your content and offers in a full-screen overlay.
Fullscreen Button Plugin, with a stylable Unicode Symbol for your WordPress.