How to add a Static Background Image
Step 1: Add the image you wish to use with the Add Resource button.

Step 2: Open the Page Inspector with the Page Info button.

Step 3: Click on the Header tab.

Step 4: Add the following text to the Header-Header Section: {image : '%resource(background.jpg)%’}

*Make sure the resource name matches the name in your resources section

Preview and you are done!