Use the css3 attribute: background-size
Background-size: cover can be stretched like a desktop Wallpaper
The w3c explanation is as follows:
Syntax
Background-size: length | percentage | cover | contain; value description
Length specifies the height and width of the background image.
Set the width of the first value and the height of the second value.
If only one value is set, the second value is set to "auto ".
Percentage specifies the width and height of the background image as the percentage of the parent element.
Set the width of the first value and the height of the second value.
If only one value is set, the second value is set to "auto ".
Cover extends the background image to a large enough size to completely overwrite the background image.
Some parts of the background image may not be displayed in the background positioning area.
Contain expands the image size to the maximum size so that its width and height fully adapt to the content area.