Preferably, an empty space with no obstructions.
The best I've found so far is Adam Miller's 2 x 2 round corner in the old CC Interior tileset.
This is for a temple, something like this:
I thought the temples of Zwerk's Roman City might work, but they are just exteriors. *sighs* Aside from that, I can't recall any others that might work.
I did a couple for the NWN2 standard tiles. But I guess that's probably not what you're looking for.

a good question to pose to zwerkules would be whether he would approve of anyone adapting his work from roman city to be used in an application like this.
I did a couple for the NWN2 standard tiles. But I guess that's probably not what you're looking for...
Academic, since it's not an interior. On the new vault that work has an open license, so open projects don't need permission to make derivative works, though of course it's good practice to credit and link to the original.a good question to pose to zwerkules would be whether he would approve of anyone adapting his work from roman city to be used in an application like this.