Plenty of manga authors look like regular people, albeit acutely over-worked regular people. Then there's folks like infamously ageless Hirohiko Araki, boss Kazuo Koike, rocking Buichi Terasawa and so on. The Attack on Titan manga has a distinctive look, and if you were wondering what inspired it, I propose that Hajime Isayama could have partially been drawing from the image starring back from the mirror.
From NTV's Future Theater
SPOILER WARNING for those following series in anime
Hajime Isayama talking Muv-Luv
Bit of an amusing bonus...