[Jim Jones]

. . . Maybe I need shorter focal length to accentuate distorsions and/or vignettes to make the images interesting. . . .

Yes. Blur is directly proportional to the diameter of a correctly sized pinhole. Therefore, you can get sharper photos if desired with shorter focal lengths. Extreme wide angle lenses are expensive, but pinholes of all focal lengths cost the same. The apparent distortion inherent in wide angle photography is a valuable tool. National Geographic often uses it.