"an enormous hand-drawn Sierpinski gasket"
Sierpinski triangle
Public DomainSierpinski triangle

Also known as the Sierpinski sieve, this is a fractal devised in 1915 by Polish mathematician Wacław Sierpiński (1882-1969).

This reference spawned a painting that featured in an art show inspired by Infinite Jest, entitled A Failed Entertainment: Selections from the Filmography of James O. Incandenza. 

Artist/curator Sam Ekwurtzel gave an interview prior to the show's debut on January 29 2010, where he explained the relevance of the Sierpinski gasket:

"And then there are a couple of paintings. One is [...] a painting of the Sierpinski Triangle, which David Foster Wallace referred to. He said that the structure of the novel was based on the Sierpsinski Gasket, this sort of structural triangles-within-triangles, and if you were to sort of magnify that structure, it would infinitely reproduce itself. The novel has this sort of leaping structure of narratives within narratives, so at any point, you can pick up the novel and start at any point, and the story will sort of repeat itself if you read it as a loop."