I assume you want the animals to be free range in there versus caged in some way ? Many people have had luck with some of the smaller dentrobatids such as Epipedobates tricolor and Oophaga pumilio. They're not exactly cheap though. Cheaper options that I know of people having luck with are the smaller Phelsuma species, Lepidodactylus lugubris, Lygodactylus species, Sphaerodactylus species and Hemidactylus species. You could also try some of the smaller Anolis species like A.carolinensis or A.sagrei. Some small tropical hylids may also work.
Something to keep in mind though.....in a new greenhouse, there is not much in the way of bioload. Small animals are far better suited for large, older greenhouses with established colonies of small invertebrates like springtails, sow bugs, roaches, flies and other small insects to keep them fed.