Only type we don't have is regen/resistance type. Hope to see that somewhere. I assumes it is unavailable at present, hopefully it will get added later.
Probably the one unknown tribble that is currently unbreedable, apart from Rivera. The Devs have confirmed that there is a bug in the tribble process stopping it from being born. It has similar visual characteristics that could make it the regen/resist buff tribble but only time will tell. They also confirmed some of the suspicious errors we found during our breeding sessions. So expect some tribble changes at some point in time.