Though I will admit that I play Federation alot more than the Klingons, I do enjoy going over to that side every now and then. Our Fleet has Mondays and Fridays reserved as our Klingon Days.
With that being said I would like to see the following things in the future for the Klingon Faction.
Female versions of the Gorn, Nausicaans and Letheans Kriosians (they are a subject species of the Klingons) Arin'Sen (they are also a subject species and also already have parts in the character creator)
Gorn, Nausicaan and Orion Ships
- These are already in the game. The Klingon Empire isn't really as huge into resources as the Federation since they mostly do rely on themselves to get the job done, and it isn't that far fetched for them to accept other ships from at least the Gorn into their ranks. It would be nice to have for variety's sake and it would make things on the Klingon-side seem more realistic - at least in my opinion. They should also come with some bridges of their own.
More uniforms and customization options for the uniforms for the Klingons! Get the concept art people to draw up some stuff. There isn't enough variety currently on the Klingon side.. though this isn't that huge of a deal.
This goes without question that the Klingon faction could benefit from more PVE and Episodic Content.. yes they are supposed to be PVP focused.. however not everyone likes PVP and there are a ton of people that like Klingons.
More PVP maps.. it gets old doing the same ones over and over again.
This is all that I can think of for now.. but things are generally heading int he right direction for the Klingons.