I'd like to build a large format pinhole camera using photographic paper as the medium. I've found several articles and how-to guides for building small/medium format 4x5 pinhole cameras but nothing on a larger scale.
The thing that changes with pinhole camera size is the best pinhole diameter to use. The optimal pinhole diameter is such that your pinhole-to-paper distance is the "Fresnel length" (please google for definition) of the pinhole at some representative wavelength of your filter bandpass. If you don't use a filter then you can guesstimate the sensitivity of the paper as a function of wavelength, consider your illumination spectrum (approximately solar spectrum) and go for somewhere in the middle.
Using the optimal pinhole diameter gets you the best compromise between diffraction blur (which increases with decreasing pinhole diameter) and the geometric "circle of confusion" (decreasing with pinhole diameter). Ansel Adams' book "The Camera" describes this in photographic terms, and college optics books describe this in physics terms.
3rd party edit: What this means in practical terms is: to get an 8×10” camera from a 4×5” design, scale all dimensions by a factor 2, except the pinhole diameter, which should be scaled by a factor √2̅ ≈ 1.414.