Copper is a metal and deserves the same treatment Iron gets in the game.
Copper Trapdoors -
Copper Pressure Plate
Copper Railing (like Iron Bars) -
Copper Doors -
Copper Plated Chains (Skip the copper nuggets and just use an ingot with a normal chain to craft it) -
Mojang can even get a little creative and use the hopper style recipe to make copper tubing/pipes. I'd also like copper Signs