There are 15 polyhedral forms in the cubic system. Most are Platonic or Catalan polyhedra (but not necessarily canonical) and 5 are unusual and appear in one or two of the cubic system classes

These are :

deltoid dodecahedron (aka rhombdodecahedron) in class 23 pentagonal dodecahedron(aka pyritohedron) in class m3 and 23 diakisdodecahedron (aka diploid) in class m3 pentagonal icositetrahedron (aka gyroid) in class 432 tetrahedral pentagonal dodecahedron(aka tetaroid) in class 23

The STL has been generated by an openSCAD script in which the shapes are defined by Miller indices. The same script can also create crystals in the cubic system from a description of the forms and their distances. Boracite is one such example. The object may need re-orienting onto a face for printing.

see my blog for further details http://kitwallace.tumblr.com/post/130274180189/forms-and-crystals-in-the-cubic-system

openSCAD code is on gitHub but is work in progress. https://github.com/KitWallace/openscad/blob/master/miller.scad

There is a customizer to create any of the 15 forms. Due to the method of construction, the preview is a bit small.