From the Super Mario Wiki
Shigehisa Nakaue (中植茂久) is a graphic artist and illustrator working for Nintendo. Prior to joining the company in 2003, he worked as an illustrator for the magazine Nintendo Dream, where he wrote and illustrated the long-running strip Dream Dunker, and also illustrated the promotional manga Star Fox: Farewell, Beloved Falco.
Nakaue is currently the primary 2D artist of the Mario series, having drawn the Peach Letters in Super Mario 3D Land and much of the 2D artwork featured in subsequent games and promotional material for the series. Due to being similar style to previous Mario artist Yoichi Kotabe, there has been a long-running misconception that these scenes were drawn by an unretired Kotabe despite Shigehisa Nakaue being credited as the sole illustrator in 3D Land.