Larry--I am certain Willem can offer a more technical explanation, but, simply put, I have found that by uploading a photo to a server independent of CAG's and then by posting the picture on CAG by inserting the URL of the photo on the CAG image-uploader (picture frame icon in each unpublished post's header), an individual can present a photo that is visible to both un-logged guests and logged-in members/non-members.
Keep in mind, though, that those photos will have a maximum side-dimension of 500 pixels, although you can click on the image to see it in full size. --Frank
FJR1's post in Visability of posted pictures was marked as the answer