For the past 20 years, there has been over one hundred Pikachu illustrations. Ken Sugimori, who worked as a character designer and Art Director for the Pokémon franchise, designed a few Pikachu illustrations for the Pokémon Trading Card Game (TCG):

10 years after the beginning of the Pokémon Franchise, rare Pikachu cards appeared. Until then, Pikachu was a common card. The first rare Pikachu card was introduced in 2006 (EX Legend Maker Set):

For the 20th anniversary, Pokemon re-released some of the first Pokemon cards. One of the first Pikachu illustration from 1999 (Base Set) was re-released in 2016 (XY Generation Set):

From Ken Sugimori to Mitsuhiro Arita, multiple designers have contributed to shape Pikachu’s design. Despite over 20 years of existence, Pikachu illustrations have proven to be timeless and keep appealing to millions of fans. Some cards like Pikachu Illustrator only exist in a few copies and are worth thousands of dollars.

Pikachu Illustrator has been created in 1998 and only 39 copies of this card were released. It was designed by Atsuko Nishida, a graphic artist who worked on several aspects of the Pokémon franchise, alongside the Pokémon creator Satoshi Tajiri and artist Ken Sugimori.
Last year, a copy of Pikachu Illustrator was sold for 54,970 dollars. Fortunately for collectors, it is also possible to Trade Pokémon Cards at a cheaper price.