Barring price and, uh, style, seems like if you're after ambient lighting then you're not going to do much better
than by embedding electroluminescent materials into your wallpaper. They don't mention a manual override, but
apparently the Solar Powered Wallpaper system features a light sensor which bumps the brightness automatically, and
draws power from both solar cells or the grid. Probably less than
ideal for the bathroom.
[Via Near Near Future]