From Bulbapedia, the community-driven Pokémon encyclopedia.
An example of kawayoo's artwork
Kawaguchi Yoohei (Japanese: 川口洋平), born 1974, is a freelance digital illustrator, and has been providing artwork for the Pokémon Trading Card Game since the Rising Rivals expansion. He is often credited by his nickname "kawayoo" (川洋) in his work.
Youhei's style is very distinctive, brought about from his creative approach and dedication to each one of his illustrations. He creates subjects from scratch by using a graphic tablet in image editing software and applying hundreds of strokes to define base shapes, outlines, backgrounds and final details. These result in often surreal, heavy, multi-layered images reminiscent of oil paintings. His images often focus on muscle tone, expression or contrast and have themes influenced by cyberpunk or anime. The Pokémon he has portrayed are often very detailed, vibrant and in dynamic positions, among which include the Pokémon C cards, which he provided all the artwork for (with the exception of LV.X variants). For a list of cards he has illustrated, go here.
Youhei also drew the promotional artwork, which includes booster pack art and theme deck art, for all of the HeartGold & SoulSilver expansions.
kawayoo's personal website