The Elder Scrolls is very much imitating of J.R.R Tolkein's work, though not all of Tolkein's work is in TES titles. What would you like to see in the future game(s)?
I will list a few things I know about that didn't make an appearance as a reference in TES titles.
1. Azog- This could be a named Falmer boss that speaks with the PC, before battling with him/ her. Unique weapons and armor could be looted from this boss as well.
2. Stone-giants- Much different than your standard TES colossus, i'm sure you can figure out why.
3. Two headed trolls- See above.
4. Ents- They are colossal humanoid tree spirits, that move much faster than typical-sized humanoids can.