In order to add a static background image to any of your slides click on the background button in the element toolbar.
Clicking on the background button in the element toolbar will open the WordPress media library, which you can use to either upload an image, or to select an image you have previously uploaded.
Click on the Select Files button to select the file, or simply drag the file you want to upload into the box. Once the file has been uploaded, click on the blue Select button – using the normal Media Library fields you can specify the alt text and description for the background image.
In order to adjust additional settings for your background image, you will need to scroll further down the page to the Slide Background section on the slide settings page.
In this section you will see a scaled down version of your slider background (without any elements), and can adjust your background positioning, repeat and sizing, or specify a background color if you choose not to use an image.
The background image can be replaced by uploading a new background image source – simply click the Add button, which will open your media library.
Finally, you have the option of switching between a static background image or one of two animation effects – a parallax or the Ken Burns effect. Switching the Ken Burns effect on will enable additional settings that control the zoom and transition direction for the effect.