When you set a background image on an element (e.g. a Container or the entire Visualization) the Background Options toggle will appear beneath it. 

Click on it to unfold available options:

Size

Set how the image will adjust its size in relation to its container element (aspect ratio will be always preserved, it won't be stretched):

• Cover: The image will adjust itself to cover the entire area of the container, cropping out past its edges.
•  Contain: The image will scale to fit entirely in the container without cropping. Blank spaces or repetition may appear when image and container aspect ratios differ.
• Auto: Uses the actual size of the image.

Repeat

This option determines how the background image is repeated. The choices are:

• Repeat: The background image will be repeated both horizontally and vertically throughout its container.
• No repeat: The background image won't be repeated.
• Repeat-x: The background image will repeat only horizontally.
• Repeat-y: The background image will repeat only vertically.

Position

This allows you to choose where the image will be anchored related to its container. Use both drop-downs to set the vertical and horizontal position. 

We encourage you to play with these options until to get the desired result!