I saw a thread crop up about the brightness of darkvision, so I figured I'd try a suggestion that is also lore-friendly (tmk)
Drow, with their improved darkvision, do end up lighting up dungeons with a pale blue-white light if they are selected. Another option would to attempt the drow heat-vision that I've seen written in a book, though I've no idea if it's canon or not (Daughter of the Drow, Elaine Cunningham). Specifically, I recall a scene where in complete darkness, drow vision moves from the light spectrum to the heat spectrum, which could possibly be implemented with a permanant outline akin to the already in-game feature for NPC outlines-- but with another layer.
Inanimate objects would be cooler, like stone or metals, while magical or -- IDK, it's just a thought!
