I've made a few posts in the past talking about my enjoyment with AD&D's Class Kit system, my take on creating class kits on the fly and my attempts at doing this in my current campaign. Dyson Logos who many know for his excellent maps has been producing a series of d12 Random subclasses each Thursday. Many of them are quite interesting, simple and to the point without undue mechanical clutter and would make a great addition to your Labyrinth Lord game. I suggest you check them out.
My personal favorite are the Elven subclasses.