This window offers you several options for designing the background of your postcard:
"Load image" 
opens a
file browser from which you can choose a background image for the postcard.
"Apply colour" 
floods the
background with colour, obliterating any image previously chosen as a background.
"Background colour" 
opens
a colour selection box from which you can choose the background colour.
"Center image" 
centers the
background image loaded from a file in the postcard work area.
"Tile image" 
tiles the image
loaded from a file.
"Stretch image" 
makes the size
of the background image loaded from a file equal to the size of the postcard work area.
