From Bulbagarden Archives

Official art of the various Pokémon species, by Ken Sugimori.

Naming convention dictates that these images are to be in the format of (National Dex number)(English name).png. Images may be moved when English names are released for the Pokémon of a new generation. If there is a replacement for the older Sugimori image, then the older one will be moved according to this format: (National Dex number)(English name) (Game Abbreviation).png.