Forum Moderators: not2easy
Unless they have invented a new CSS command backgrounds do not stretch. You can set your background to repeat on the X or Y axis (X is horiszontal and Y is vertical) or not to repeat. If you are using no-repeat or repeating only on the X or Y axis you have the added command as to the location of the background image.
You might want to Google "tutorial CSS background position" for further information.