Elizabeth Caudwell suggests that that Seyb's "gestural way of approaching painting may in some ways be attributed to his grounding in manual work". While Seyb is best known for his evocative, vibrant New Zealand landscapes, his subject matter has varied from landscapes to portraits, from abstract works to impressions of Bob Dylan. The consistent quality is Seyb's bold, expressive style, a thick and textural mark-making that records the physical tracks of his brush as it energetically trails colour.

In 2008 Seyb was invited by the Caselberg Trust to complete an artist residency on board a yacht as it sailed through Fiordland. The resulting body of work formed a suite of powerful paintings capturing the mythical, brooding grandeur of the region as well as the rich intensity of its golds, greys, greens and blues. For Seyb, however, the landscape is resonant with more than its impressive visual qualities: "You have to have an imaginative hook to look at the landscape because otherwise it is just the picturesque, I like to look at it as something symbolic. It gives a more symbolic edge to the landscape which is what inspires me to paint."