I did a little bit of macro pinhole (defining macro as 1:1 or greater). Here are a couple of pictures using my 25mm 120 film pinhole with objects at 25mm distance from the aperture. Due to the tight conditions, I used objects that I could backlight instead of front lighting:

627614743_sFUFj-L.jpg

627614718_Grhm3-L.jpg

Macro math on a pinhole is simple - for 1:1, the focal length is equal to the distance to the object.