Reddit reviews Canvas Enamel Pin Display Banner

Shadow boxes are quite popular. You can get some from your local craft store, back it with some cork or cardboard (though the structural integrity of the cardboard will decline over time as you stick and restick pins on it), glue some felt over it, and boom: instant classy display case.

Another solution if you don't want to get crafty is cufflink display boxes. You can lie them flat on your desk or prop them vertically. Double-posted pins may present a problem if they don't align with the crevices where you'll be wedging the pinbacks.

There are also pin display banners you can find for purchase online, or make yourself if you know your way around a sewing machine. Those tend to be thick canvas or heavy cloth with wooden dowels and some string for hanging.

Your cheapest, fastest option is probably a cork bulletin board, as /u/CorayEel mentioned.

Happy pinning!