If I recall correctly those are real pictures that were taken when she was cast in Apocalypse Now as a playboy playmate that would feature in a scene entertaining the troops. They took a set of pictures to be props that were essentially supposed to be fake playboy centerfolds that could be on the walls in scenes. The pictures were real but the issue of playboy was fake, created just for the movie.
However, Lynda Carter had to drop out of the movie and was replaced by Coleen Camp and new 'fake' centrefold shots had to be taken for continuity. The prop shots still existed though. People often say that the Lynda Carter ones are Carters face superimposed on Camp's body from those pics but while they are really similar you can easily see differences.