Images and shapes can be layered so one image overlays another. With an image on the ‘back’ sheet and text on another sheet combined you get a document with an image plus text overlaid. When the sheets are put on top of each other you see the finished document. Each sheet contains images or text that you can adjust without changing things on other sheets. Think of layers as like a series of clear plastic sheets on top of each other. They aren’t as complex or powerful as layers in image programs like Photoshop but Word has layers all the same. Insert a picture into a Word document and send it to the back of the document layers. The solution is to forget about Word’s Page Background feature and use another method that gives you more control. Note that the ‘sample’ in the Insert Picture dialog above bears no relation to what happens in the document, Unless the picture is exactly the same size as the page, it’ll probably look wrong. There’s no provision to resize or reposition the page background image within Word.
If the image is too small for the page, the image is repeated. What you see on the Word page is the top left corner of the image.