Frogview.com has a collection of trompe l'oeil paintings and images that will delight math nerds more than serious artists. Hat tip to Steve Higgins at OmniBrain, who gives the apt title, "Visual Illusions in Fine(ish) Art."
For real art that uses a bit of deception, check out Chris Jordan's stupefying images. This one is "Cans Seurat," made up of "106,000 aluminum cans, the number used in the US every thirty seconds." View the whole thing, or else. Hat tip to Project Sanguine.