Hello koriwj,
What you are tying to do is typically called a watermark. This is where you will have an image at the back of the page, and be able to have type or other images on top of the image. Also, if you add more pages, the image repeats.
You can get more details on how to mange multiple images in a multiple page document using Section Breaks. From the menu bar, choose Help > Pages Help > search for Watermark.
Here is a sample of what I did.

To insert an image as a watermark.
Click on Insert from the menu bar, and click on Choose
Navigate to the location of your image, click on the image, then click on Insert
You may want to modify the image but adjusting the increasing the exposure, and reducing the saturation. That's what I did for the Blackhawks Charities logo.
Once you have the image managed and located where you would like it, click on Arrange from the menu bar, then click on Move Object to Section Master.
That should do the trick.
I hope this helps you out.
Regards,
SoftwareAddict1462