I was looking at some MM7 sprites when I noticed something
MM7 uses no less than four differently styled sets of Dr. Wily sprites during the game!

From left to right, there's in the UFO, in the Wily Machine, Wily on his own, and in the Wily Capsule
UFO Wily has super detailed hair that's also shaped similarly to his MM1 artwork. His skin also only uses two shades and an outline colour, wheras the other Wilys use three shades and an outline colour. UFO Wily's mustache is also "poofier" than the other Wilys
Machine Wily has a noticeably large forehead, making him seem somewhat off-model. His pupils are smaller than UFO and Capsule Wilys, and the same size as "normal" Wily. While not a lot of hair is visible, it seems to be less detailed than UFO Wily's. Machine Wily also has differently shaped ears than the other Wilys
"Normal" Wily is the one we all know. His hair is a bit more like how it's supposed to be in post-MM2 games, but still not quite the same as how it's depicted in artwork. His face is detailed somewhat similarly to UFO Wily, except with bigger eyes and a droopier mustache. Also with softer shading and no shininess on his forehead
Capsule Wily, I only included because his hair is the closest to the hairstyle that Wily has in all the game artwork. Additionally, he has some oddly large pupils when compared to the size of the rest of his eye
and that's all for a ridiculously long comparison of dr. wily sprites from a game that many people seemingly don't care about