The tank would be perfect for some pictus geckos, but not big enough for a crestie. I don't know if it would be big enough for a rosy, but if so, go for it! They are great snakes if you know how to take care of them.
Hognose would be cool too, but I do think the cage would be a bit small.
Fraid I don't know much about turtles...
I say pictus or rosy boa!