They are both black and white production photographs signed by Linda Blair. I don’t recall ever seeing these photographs ever before.
The first (above) gives us a close look at the prosthetic tongue Linda used in The Exorcist. She is poised at the bottom of the stairs where the spiderwalk scene took place, which may indicate why this became so rare because the spiderwalk sequence was not used in the original release of the film. Linda is looking into the camera, a clear indication this is a production photo.
The second image (below) seems to depict Linda either practicing the “You’re gonna die up there…” pee scene, or an alternate take in progress. She is hiking her nightgown up to reveal her ankles; a pose not used in the final cut of the film.
Fascinating to see images like this still surfacing after all these years.