Do you know we’re not quite sure how the original Will-o’-the-Wisp or Jack of the Lantern lights? Gourds were the earlist planet domesticated by humans but perhaps Jack-o’-lanterns were first carved from turnips as the Halloween practise probably started in the Highlands of Scotland. It’s not the container that matters.
It’s your ability to make the lantern look like a spirit or goblin. With that in mind… why not tree stumps? Stumpkins!