Well, non-lore elements can be distinguished in 2 groups:
The one I call fanfiction, which fills the not well-known and unknown parts of the lore in the direction of the "coolness". See BFME, LotRO etc. and the other one, which I call creative fiction, that fills the gaps with well-reasoned and thought elements, using the most logical assumptions and parallells compared to RL.
Plus, someone may consider a settlement in Eriador that isn't mentioned as a non-lore element, while another one may say that in that place, because of its importance (strategic/economic etc) there should have been a fort or a settlement.
All in all, to finish with my nonsense, I don't think that the team will give a really satisfactory response in your question