AddThis provides a number of built-in background images that can be used for the Audience Targeting Overlay position, but it also allows a custom URL to be provided for the background image. When selecting a background image to be used, it’s important to know the size guidelines that should be used when selecting an image.
The Audience Targeting Overlay has a width of 640 pixels, with a variable height. We recommend using an image size close to 640×480 pixels. The image is centered on the x-axis (horizontally) and is top aligned with the y-axis (vertically).