I live in Florida, where a carved jack-o-lantern can rot to goo in a matter of days.
For inhospitable climates (and just for fun) create eyes, nose, and mouths from thin LED-lined plastic or fabric of some kind. Make the LEDs able to change colors, or blink in patterns, or react to motion. Add sound effects for even more fun.
Attach them by pushing them into pumpkins with spikes on the back, or stick them to elastic bands and stretch them around the pumpkins.
They’d be reusable year to year, no carving required, and they’d work on pumpkins, gourds, trees, or whatever you want.