Word 7 allows you to print a very faint image 'behind' your text - called a 'Watermark'.

To place a watermark on your page, insert a graphic as usual, and select Format Picture (right-click on the image).

On the Picture tab of the dialog box, under 'Image control', select 'Watermark' from the Color box.  The Watermark preset settings simply adjust the brightness and contrast settings of the image.  To format the graphic so that document text flows OVER it instead of wrapping around it, on the 'Wrapping' tab, click 'None'.

This Watermark will only appear on the one page, of course.  If you wish it to appear on every page, you will need to insert it into a persistent element, like a header or footer - though this limits where on the document the Watermark can be placed.