Prior to generation V, we didn't have Pokemons based on polar bear, centipede, leopard, vulture and ant. Then Generation V brought out Beartic, Scolipede, Liepard, Mandibuzz and Durant, respectively. This is tendence for the next generations, soon all the animals will have at least one Pokemon based on them, and Nintendo will start creating different Pokemons for a same animal.
Well, post ideas of animals (or objects ^^) that haven't been turnedo into Pokémon yet. I'll start out with two suggestions: