The question can also be raised: Do you mean strictly canon Klingons, or Klingons throughout all ST media? and more to the point modern or all through Klingon history?
Historically I would imagine cultures similar to Samurai of Feudal Japan and Vikings of Norse Europe. But also the military tactitions of the humans Roman Empire, the Mongols of pre and post Genghis Kahn, the idea of the cossaks, and also many of the "non technological" societies such as the native Americans, Picific Islanders, Celtic tribes, etc. Since Klingon political views varry as much, if not more than, Human views, I imagine there were a few more peaceful clans. That the existing empire wide feudal, warrior oriented system survived is an indication that the peaceful nations fell to the warrior nations, and possably long before Kahless rose against Molor. It would also not be suprising to me that of all those various warrior styles, with their wide range of systems, that not all of those tribes would have been a feudal system.
Then, given that the Klingons were very naval throughout history, (stated in an ep of TNG) there were probably some Klingon cultures that were similar in nature to England, France, and Spain. Imagine Trafalger and Lord Nelson as being on Qo'noS ( or if you prefer Klinzai)
Too much info? Maybe I should just write a book. "The Socio-political History of Qo'noS: Pre-Kahless through the Klingon Empire under Martoq"
