Can anyone point me to information about valance lighting? I'm
interested in the sort that run parallel to a wall, close to the
ceiling, and throw indirect light on the ceiling, as well as washing
the wall below the valance.

I see these in many discussions of lighting, but I can't find any
information on how they are built. Are they fabricated on-sight from
standard construction materials? Are they prefabricated and simply
mounted on the wall?