"Carpet Pages" were purely decorative, and were so named for their resemblance to eastern carpets. This carpet page from Folio 27v of the Book of Kells depicts the symbols for the four evangelists: Matthew the Winged Man, Mark the Lion, Luke the Calf (or Bull), and John the Eagle, derived from the vision of Ezekiel.
Just for fun, you can solve a jigsaw puzzle of part of this image here at the Medieval History site.