These days "tiki mug” is an umbrella term, used for all ceramic sippers with an island aesthetic. but Kirsten sees it more as an eBay buzzword. “Simply put, a tiki mug should depict a tiki" — which Merriam-Webster defines as "a wood or stone image of a Polynesian supernatural power." Says Kirsen: "A mug depicting a skull is a skull mug, a mug sculpted like a rum barrel is a barrel mug.”
Just something to keep in mind.