In updating from some Walmart style particle board and veneer type shelving units to something more durable and interesting, I decided on the industrial design appearance of shelves made using steel pipe and fittings as the supports. The internet is crowded with photos of this style, but I wanted mine a little different and made them lighted with a little steampunk vibe. I also used my water valve light switch, which is an Instructables featured project you'll find here. I recommend doing this using 12V lighting to avoid safety issues, but remember that the wattage capacity of the switch at 12V is reduced. At 12 volts the switch is rated for 5 amps, so that's a maximum of 60 watts. At 120 volts the switch is rated for 3 amps, so that's a maximum of 360 watts. At 120 volts, as this project is, I'm not comfortable going over 150W because of the small gauge wiring used. Unfortunately, I was unable to find any 12 volt vintage bulbs.
After having built this using 1/2" pipe and fittings, I highly recommend doing any sections that require wiring to run through them to be 3/4". It was verify difficult to pull the 16ga wire through the 1/2" pipe and fittings I used and also have room for wire nuts to make connections. If I were doing this project again, I'd use 3/4" throughout.