Each time you crack an egg open, instead of tossing the shell into the trash, drop it into an open container that you keep in the fridge. When the container is full, crush the shells into small bits and sprinkle them around the base of your plants.
If you still haven't found a vertical planter idea that is exactly your style, maybe this one will do it for you. The pots are simply held in position by a single piece of rebar put through the drain holes of the pots. Perfect for small herbs!