For info, I knew at least one rpg game built on top of wesnoth's content and lore:
Heroes of Wesnoth. Well, it was far from being complete, 0.1.x are usually alpha/pre-alpha, and this shows up there. I don't think it's still developed either. And it's really based on wesnoth's assets, probably not a lot to "salvage" from there
There are also several RPG content built for wesnoth, the most rpg-like being those built by a modder named "bob the migthy", but they are made to be multi-player, up to 5 players. Dunno if those things would be usable for an example suite though: it's pixel-art stuff based on an already rich base (wesnoth does have a quite impressive collection of game assets in core, even if you remove the assets that are no longer in current stable), One would need to create the 3D models for it, which would probably takes *a lot* of time.
On the other hand, I must admit I don't know any 3D content with licences compatible to DFSG (seen in previous thread it's a must), so it will probably have to be done, but I think it might be a good idea for an "example suite" to have stuff reusable, and thus imported from other projects.
Well, I guess if the direction is to go medieval fantasy and the likes,
Flare's content or some of
OpenDungeons assets could be used, either as placeholders or not.
Can't think of any other 3D game's content that would fit (either for theme or for licencing)... At least, with flare's or OD's contents, the styles might be relatively consistent, since they were mostly built from their specific game (well, for flare, I think one of the goals was to produce assets other could reproduce, too. For OD, I don't know, never really went into it).
Damn. Long time I used the phpbb stuff, reminds old times.