Is there a common/official name for visual puzzles that are based strictly on the observation skill - like the common "Where is Waldo" pictures, "find all faces", "count all X in the picture (or find a given number of them), "Spot a thief" and the likes - where the visual mess or tricky composition of the image obscures the location of the puzzle target?
In the online realm, these are known as "hidden object/picture" games, and the definition also matches those which appear in books. From Wikipedia (emph. not mine):
A hidden object game (sometimes called hidden picture) is a genre of puzzle video game in which the player must find items from a list that are hidden within a picture.
In essence, "Where's Waldo" is just a simpler version of this game, in which the list of items you are looking for has a length of one (though if I recall, there are sometimes more objects to find in Waldo).
Physical copies of these games also, I believe, can go by the same name.