Right when I I looked at this picture, my brother put on the song "Say what you will" by Black Label Society... and as background noise it fits this perfectly!!!
Well, alicorns shouldn't really count as a distinct type of pony, but instead are supposedly just a combination of unicorn, pegasus and earth pony all in one body.
Also, and this is more so just a personal head-canon, but I don't think crystal ponies represent a distinct tribe, or at least not a natural one. Note that at the end of the S3 premier all of the M6, plus Cadance, Shining Armor, and even SPIKE take on the same kind of crystal forms, all be it only temporarily. As such, it is my theory that the ponies of the crystal empire were originally just earth ponies who after generations of exposure to the ambiant magical energies from the Crystal Heart have become more permanently altered.