Much of Isherwood's early work was done for Marvel Comics, including such titles as Silver Surfer, Conan the Barbarian, Daredevil, and Doctor Strange.

Since then, he has been involved in movies as a storyboard artist and a concepts/production illustrator, working with the likes of Bryan Singer, Richard Donner and Darren Aronofsky.

[3] He has also painted and designed covers for Canadian publishers, including Ann Diamond's Dead White Males (2000) and Sand for Snow (2003) by Robert Edison Sandiford.

In 2011, Isherwood illustrated and prepared the cover for the American novel Antiquitas Lost, by author Robert Louis Smith.

[5] In 2015, Geof began teaching part-time at Algonquin College in Ottawa, Ontario, in the School Of Media And Design.