They are (arguably) Pokémon that I use or have used in my Twitter banner. Will edit any other used images into this entry.
They've been down-scaled to save space and file size.
An unused design that ended up being cut for 2 Generations.
This design was first seen by players in the Gold/Silver '97 Spaceworld Demo.
It was later discovered to also be cut from the prototype versions of Generation 1, and never made it