You have to turn on reflections, or they won't work properly.
There are some reflective walls and floors at
TSR (
booty - millenium-reflectivewallsfloors.zip) by Murano. Comes with a shader file you'll need. Can't think of any other set (but there might be).
Only tested them once or twice, and they take lots of memory to run properly. Slowed down the lot a great deal (a downloaded lot with reflective floors everywhere). The very first thing I did to the lot was to remove all the mirrory items... It's nice if you want to take pictures, but not for playing with...