Deliberate choice of word. The silver is an outline, so it draws the flames. "Lining" would also work, although that sounds a bit more like one side of the flames to me. (Mind you, I've hardly ever seen "limn" used outside D&D, where it is used specifically to describe flames around the edge of something. Given the rarity of the word in other contexts, and the spread of D&D, you could make a good case for meaning shift.)

As for the cause of the shrine fire…