Holmgren first started as a cartoonist for Shadis Magazine, where his strip, Joe Genero: Adventures of the Average Man, debuted in 1990.
Holmgren is responsible for several cover illustrations for the early issues of Jolly Blackburn's popular Knights of the Dinner Table, and contributed to the design of the character Sara .
In 1998, Holmgren co-founded Sanguine Productions, and a year later produced Ironclaw: Anthropomorphic Fantasy Role-Play.
[1] Despite the 2000 release of the third edition of Dungeons & Dragons and the subsequent marketplace dominance of the d20 System, the Ironclaw game found a small but solid core audience.
Holmgren served as head designer and art director on later Sanguine projects, including Jadeclaw, Albedo: Platinum Catalyst, and Usagi Yojimbo.