Sometimes when a lot/land is for sale an agent will draw on the photographs to indicate certain aspects of the property or utility supply. I've seen water well circled, access roads pointed out and where electricity is stubbed out.
Normally the photo will have an explanation/legend to the side as to what the markings mean and what they stand for. It's similar to reading a map or a blue print. There should be directions so anyone who is interested can clarify details in the photos.
Or it could be part of a happy face :)