Depends on which version of Word but the principle is as Shas says. View Header & Footer. Insert a text box that stretches from the header to the footer. Insert your picture, right click it and format it as a watermark, ("washout" in Word XP), resize it to suit your page. The text box will now have shrunk to the size of your picture.Drag the text box to your chosen location on the page. Format the text box and remove the border line.