Changing the background can be good for setting the subject of the publication that you are attempting to present. Adding a good image can be a good start to making a first impression.
Note: Please ensure that the images you use during your publication are of good quality and high resolution, using a lower resolution image and trying to make it larger may ruin the image quality, causing it to blur or pixelate.
To add a background image, simply click the Add icon in the top left of the editor. From here click the Images tab, then click and drag the Background Image element onto your publication. You will then see the element in your publication with the image icon covering it.
Select the image element and you will see that it is tagged as Image in the bottom right in a Cyan Rectangle with grey text. You can mouse over this and more options will appear, the options of Image, Video, and Color will appear. Click any of these you would like to change the background type too.
On the right side in the configure tab, you can then edit the element further depending on which type you have selected.