The following images are part of the 'Columbia University Image Library'
(aka COIL-100, at http://www.cs.columbia.edu/CAVE/software/softlib/coil-100.php):

  - car.ppm
  - cup.ppm
  - duck.ppm



The following images are part of the 'Caltech 256 Dataset'
(http://www.vision.caltech.edu/Image_Datasets/Caltech256/):

  - bear.jpg
  - dolphin.jpg
  - monkey.jpg
