What can live in a 12x12x18 terrarium?

Are there any snakes or other herps that are well suited to a 12x12x18 terrarium? I have an empty one.
I've thought about a Crested or Gargoyle gecko, or some type of frog. I'm wondering if there's anything else that could go in there.

Crested, Gargoyle, Dumpy Frogs, Red Eye Tree frogs.

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Certain species of day geckos would do well in those.

I wouldn't do an adult crested gecko in a 12x12x18, personally; it's on the small side for a adult to really have enough room to jump and climb. A juvenile or a sub-adult would do fine but you'd want to upgrade once the critter reached full size.

I don't know for sure about gargs but I imagine the adults have similar size requirements to cresteds, they're relatively similar species in terms of husbandry IIRC.