There seem to be TOS Klingons, QuchHa', and TNG Klingons, turtleheads.
The Motion Picture and other TOS movies had 'reduced ridges' Klingons. They are usually talked about as turtleheads, but they don't have the distinctive ridges or the hair of Worf-era Klingons.
FASA had the lovely four different types of Fusions, an idea that ENT tossed out. Then there's the Kumburan and Rumaiy, Kamorh'dag and Gevish'rae.
I'm so over the whole forehead thing.
I'm sorry - FASA?