If your games are already boxed, I would recommend just getting plastic slips they are the same price and still display your boxes. If you are mostly loose then I guess it could be handy for N64, what with its lack of spine-art and all, but I still don't really see the point for SNES.
At least some of the generic Chinese vendors who make plastic box protectors also make cartridge sized plastic protectors, which can be found on ebay. Then you can resize and print out cover-art from the sources mentioned in that old thread, if you want, or make your own.