Right click on the desktop, select Desktop Appearance..., select the Background tab, after selecting which picture you want choose the appropriate style, I find that Zoom or Stretch often fill the screen with a picture.
I'm talking about Nautilus, the file manager. It has backgrounds you can use in the fileview. Instead of using the tiled backgrounds that one normally does. I would like to use a bigger image, like a standard wallpaper as a background in Nautilus instead.
If you open Nautilus and click "edit", you will see the menu item "Backgrounds and emblems..." It allows you to insert a background image (usually a standard pattern which gets repeated) Or a color instead.
In ubuntu there is a file called "nautilus.css" which is able to define the "repeat" property for the background. It basically means turn on or off the tiling effect.
Whats actually happening in Nautilus is that I use a background (my own wallpaper) and it looks right. Then I close Nautilus, and open it again later, only to find the image has been tiled.