I read the paper entry as anything that is portrait shaped (which your linked photo is). Portrait the word, can mean both of a person or describe paper orientation - e.g. when you print anything you choose the orientation of the paper as either "Portrait" or "Landscape" - it is a bit confusing but the paper orientation words probably came from fact that portraits of people were normally done with the paper height greater than width, and landscapes/scenery with the width greater than height. If the paper didn't use the words "it just has to be up and down (portrait shape)" then I would have assumed portrait of a person etc but it seems that is far more open than that and can be anything on a portrait orientation postcard size.