Select the location. It can be "First image" or "Second image". The "Second image" is on top of the "First image". Two image locations are required to support items with dynamic width.
Select this to use external image file. When the navigation bar is inserted into the active page, the external image file will be imported to the website automatically.
The image will be compressed first before conversion to make it smaller. Embed small images only and avoid embedding large images as this will increase the size of the style sheet. A Base64 encoded image is about 30% larger than the original one. Your page may be able to load faster as there is no extra http request to get the image.