Our design counter(s) are a medium gray, shortloop commercial carpet. We used a marker to dye a small black dot where the center of the viewfinder image is located. It is fairly easy to line up the objects with the edges of the camera image prior to taking the picture. We use 4" mat samples, so that can be our distance gauge.
Because the camera is mounted on the 10ft ceiling grid of a fluorescent fixture almost identical to John Ranes, we had significant glare problems. A custom fabricated from foamcore and matboard (2x4ft) set of louvers is attached below the bulbs. Solved the glare problem because no part of the bulb can be seen looking up from the design counter, but all the light is still in the room. Still working on a permanent variation to the louvers, but customers never notice the "rigged" setup.