We see the skull in a variety of contexts across cultures and periods of Mesoamerica. As such, it has a variety of meanings. I did just read a great chapter (1) about the tzompantli "skull racks" often seen on Mesoamerican ball courts: it talks about their symbolic role in the cycle of resurrection, which involves, as you said, both life and death.

Our best version of this resurrection cycle comes from the Popol Vuh. In it, Hun Hunaphu and his twin challenge the lords of the underworld to a ballgame. They lose, and are decapitated and dismembered. Hun Hunaphu's head is placed in a dead calabash tree, which then grows the first fruit. He later spits into the hand of the young moon goddess, impregnating her. She gives birth to the more famous, second set of Hero Twins: Hunaphu and Xblanque. They again challenge the lords, first losing and facing decapitation, but their heads are replaced with gourds from the same calabash tree. Through trickery they defeat the lords of the underworld. In earlier versions of the myth, they then restore Hun Hunaphu, as the Maize God, to life.

How is this represented in the archaeological record? The Maize God's ressurection is often seen in Maya art. (Note the central skull.) Disjointed human bones can be found buried beneath ball courts. Ballcourt markers also often feature a quatrefoil pattern (see here, pg. 28) that represent a portal between worlds. In creating the tzompantli, what one may call skull trees, the Mesoamericans were representing this myth of resurrection.

Another perspective (2) on tzompantli is that they were simple expressions of power, at least for the post-Classic Maya. Classic Maya monuments showed a city's ruler capturing an elite from another city. Both captive and captor have an array of names and titles. If they defeated someone important, they wanted to show just how important they were, since that makes them look all the better. In later times, this form of propaganda became less personalized- hence the tzompantli.

If you've got any specific examples of art you were interested in, I'm sure I or someone else could help you.

• 1: Ruben Mendoza, "The Divine Gourd Tree: Tzompantli Skull Racks, Decapitation Rituals, and Human Trophies in Ancient Mesoamerica" in Taking and Displaying of Human Body Parts as Trophies by Amerindians

• 2: Virginia Miller, "Skeletons, Skulls, and Bones in the Art of Chichen Itza" in New perspectives on human sacrifice and ritual body treatment in ancient Maya society

Your question focuses on early Mesoamerican art, but when you look towards more modern Mesoamerican expressions of skulls, it ties into religious beliefs and particularly folk religious beliefs quite a bitt. The skull carries death with it, and death is a powerful force in life. It provides protection in all forms, grants favors, and is petitioned for blessings or even revenge. A perfect example is the representations of Santisima Muerte/Holy Death in Mexico, which is a folk saint represented by a human skull or full skeleton dressed in robes or often a wedding dress. The lore around her says she's a Mesoamerican death deity basically in disguise (Mayan, I think). Her presence isn't feared, though she is appointed considerable power.

I hope this isn't too far afield for your question!