Ryo Ueda is my favorite artist and probably is the main person when it comes to 3D illustrations. I certainly think they took over that mantle after the passing of Keiji Kinebuchi. These are just some of the promo cards listed but his main impact has been the 3D illustrations during the ex era. They are super underrated due to being a bit of polarizing figure with regards to their artworks.
So many great artists have been mentioned so far (especially Hajime Kusajima)!
I’d love to see some modern artwork from Noriko Hotta, whose last illustration was in 2012 (though they were more prolific during the HGSS era). My favorite is their Raikou!