I'm bumping this up because as a spice girl, I would love at least 17 spots for the spices. Please don't leave out the allspice as part of a spice in the rack. We need 17. Like the OP said 16 is not prime! Tsk tsk! :P
I don't bother with the spice racks at all. Why take up all that extra space, especially for spice types I hardly use? I just carry around stacks of allspice and a grinder in a bigger bag, and make the other spices only as I need them.