While they aren't nearly the biggest images to be taken by a pinhole camera, the pictures photographer ShiKai Tseng capture are equally impressive. He employs 3D objects as the film for his 2D images in a process he calls, "PhotoGraphy".
The object to be used is coated in an emulsion of Liquid Light to make it light-sensitive, placed in a pinhole camera box, and then exposed for up to an hour. The item is then developed, just like normal film. Tseng states, "It's not from three-dimensional to two-dimensional, but 3D to 3D. So I think it's a translation, not a reduction." [Vimeo via PetaPixel]