I toyed around with the idea when I was also doing those experiments in a matching N64 cover style. I thought it would be cool to have NES, SNES and N64 all line up nicely and have a matching look, with enough differences in color and logos to be identifiable. This early spine is as far as I got. I made the top and bottom gray/silver because that's the color that comes to mind first for me when thinking of the NES (like black for SNES, red for N64). I figured the color of the middle of the spine would match whatever color the spine was on the original box art. In this case, Super Mario Bros. 3 had a yellow spine.

I tried to think of some kind of identifiable "symbol" for the NES that would go at the bottom of the spine. The problem is I couldn't think of anything so I just grabbed a closeup of part of the NES controller. Maybe someone can think of a more identifiable NES symbol to match the SNES and N64?
I won't get around to making a matching NES template anytime soon, so if someone else wants to give it a try, I'd be very interested to see what they come up with. Feel free to modify the SNES Fusion template I uploaded here.