I made a floppy disk coaster a while back and decided it would be a good design for a filament swatch as well. The swatch is 50mm square, 2mm thick, and takes about 23 minutes to print at .20mm layer height. And where you would normally have the label is a great place to write what your filament is. 

I also made storage containers with dividers (like way back in the 80s and 90s) to help organize everything. There are 50, 75, & 100m length containers depending on how many different filaments you have.