The early sources on the Palantiri are scarce; they only show up in chronicles of the late Numenorian period as gifts of the Noldor to the Faithful. In a fragment of the Red Book, Peregrin relate a tale that Mithrandir speculated that Feanor himself made them. It's possible that the great smith sent this as a joke to his kin, but I would cont that as unlikely given that his relationship with his fellow Noldor were strained, except with his sons, whom he demanded obedience. It's also possible that they were made by Celebrimbor in Gondolin given that he already established his jewel-crafting bonafides with the Elessar and the seven stones fits within the hepta-focus of Gondolin culture, but the master stones' presence in Aman works against this theory.

The cat tale probably grew out of the fact that the Faithful used the Palantiri to succor themselves in a trying time, so a cat picture would not have been entirely out of place with this this apocryphal story.

Hopefully an Noldorian scholar can chime in here and help explain this facet of Eldar communication technology.