If Geolocation is enabled:
Header search image changes based on your location, if you choose to share it and an additional image is provided. To provide an image you have to go to Dashboard > Appearance > Countries, lets say you have an image with an ID of 50 that represents France, you have to write France:50 and press Set country data and save the changes.
If Geolocation is disabled:
You’ll have to provide a default country/city at Theme Options > Geolocation and an corresponding image for that country, same as you would do it if geolocation was enabled. This means that users won’t be prompted to share their location and only one header search image will be shown to all visitors.