Earlier in 2015 the Pokémon Company ran a competition for Pokémon Art Academy on 3DS, with the reward of having artists’ work displayed on their very own Pokémon trading card. Each winner was given a custom 100-pack of Pokémon cards featuring his or her artwork! One artist, James Franzen, shared his custom pack of Tangrowth cards.
Very cool! The official competition page features all of the winning artwork. We haven’t gotten to see any others on the actual cards yet, but hopefully they may crop up soon. Unfortunately these special cards are only intended for the artists, so don’t expect them to show up in any official TCG booster packs for now.