Create your background as a "watermark" (as described in “HOW TO: Create a
Watermark in Word 97 and in Microsoft Word 2000â€
http://support.microsoft.com/?kbid=211324), but instead of creating it in
the header (anchored to the header paragraph) create it in the main body of
your document and anchor it to a paragraph that will be on the page in
question.
Two other thoughts:
1. If the background should appear just on the first page, use the
"Different first page" setting in Page Setup (Layout tab) and anchor it to
the First Page Header. This will provide a lot more protection against being
accidentally deleted.
2. If you have already inserted the background (watermark) in the entire
document, View | Header and Footer, select the background and Cut (Ctrl+X),
then Paste (Ctrl+V) on the page where you want it to appear.