When you select an image to add to a Moodle page, you can choose images from those that you have already uploaded in Moodle, or you can upload a new image.
A less obvious feature is the ability to link to a picture that is hosted on another website. For example, you can link to a picture hosted on a Flickr account or the one that appears on a non-profit educational website. If you are using pictures hosted in another website, you can add the link, but be aware that link addresses change often. Also, be sure to give credit.