Environment idea(s), Magi College, Ruins
What I've noticed in a lot of fantasy games is that there's always that infamous "Library level" I kinda want to put that idea forward, but give it a bit of a spin and make it something along the lines of a school instead. Running through classrooms and corridors, battling possessed/evil students (or if you're an evil character) ransacking a school and taking down the headmaster. Not only could there be mobs such as flying books and such, but it also adds the opportunity to see more interesting environments. School isn't all about books and study (Especially ones in a fantasy setting) Things perhaps like herbology classes, courtyards, astronomy classes, arcane study. All of these concepts would help add some atmosphere to the setting, and could even provide some interesting lighting effects. We've got Caves, Crypts and Castles, but not a lot that dabble with being outside, or simply in a more common setting, such as a school /college. Just some food for thought.
There's usually always this sort of setting for games in the fantasy genre, but instead of thinking about a ruin that was penetrated by trees and filled with forests, instead think more of an environment that the forest actually grew over and won against. Clearings, and sparse landmarks of an old civilization, perhaps standing relics and statues littered about the cluttered wood, and rather being sectioned off by big corridors, instead would be more of an area where dense trees cut off in different areas. Parties start on one side of the forest, moving through the trees and taking different paths and must reach the end. (Of course there still could be "hallways" of trees connecting some paths, but this is meant to be kept to a minimum.) Bandits hiding in trees and maybe hollowed out logs holding "Phat loot"