More ideas from Danduk
Make wooden cubes out of 1-1/2" stock and drill 1/4" and 1/2" holes in each cube to fit various bits in for storage.

Router Bit Storage Solution - I would change the design to make them interlock. shaft on top, shaft on bottom, and then interlocking pins and holes in the sides. For large bits, the holders can be the size of 4 small blocks.