Easy Backstretch (easy-backstretch) free WordPress plugin

Upload your image(s), set the Fade In effect, the in between slides time duration and the div you would like to apply the backstrech.
Backstretch is a simple jQuery plugin that allows you to add a dynamically-resized, slideshow-capable background image to any element. The image will stretch to fit the element, and will automatically resize as the window/element size changes.