The real world is a gold mine of unusual flora and fauna that can really spice up your setting. There was a documentary on Madagascar on the BBC, IIRC, narrated by David Attenborough, that showed some really cool plants and animals that would fit in nearly any fantasy world. I've always felt the American southwest is also a great source of material for Dark Sun or any campaign with a desert. There are places there, that while technically are deserts, that are teeming with interesting plant and animal life.