Are unlikely, awkward animals or objects fused together/being one pokémon on the list? You know, something like a cat being allergic to itself or an ice type with a fire sac in its body. The closest pokémon that comes into my mind when its about this, is probably Garchomp (shark+dinosaur). But its understandable because Garchomp's probably a landshark. I can't seem to remember any other pokémon with this being the base of their designs.
One thing to remember about this list is that it's sort of like a component list. Sure there are plenty of things you can solely make a Pokemon out of, but for things like Concepts and Objects they'll probably combine it with an animal or if a mythical creature is too vague in detail they may make their own version thus making it a hybrid.
But that's not so rare in psychic Pokemons though.
Even Jynx and Gothitelle are shown to do that. (Remembering every detail even after 10 years)
So I wouldn't think they would make a Pokemon solely for that.
As I said above, Eidetic Memory is something which probably won't be the only thing the Pokemon is solely based on, just the gimmick it will use. Yes, many Pokemon, especially Psychic-types, has excellent memories and can remember precise details, but that's just a side thing mentioned in the Pokedex. For example, maybe an Eidetic Memory Pokemon not only can remember precise details but is also able to project those memories and maybe is even able to read other's memories and uncover little details that being had forgotten about but their subconscious has stored away.