A lot of people call the 2nd effect an "anagram", but this isn't quite correct, as I think that term is reserved for images meant to simulate a 3D effect using two-color glasses. Be that as it may, I think it may be the term most people use for it.
Personally, I would call the 1st effect, "The Catholic Confessional".

No disrespect intended -- but if you have ever seen one in a movie, that's the view the priest is supposed to see, LOL.
T