Japan has had access to the Photos with Mario App since April, which is basically just a special AR program that allows you to unlock special Mario themed eShop cards. Starting today Nintendo is rolling the program out in the US, featuring Mario, Peach, and Goomba cards for $10 each. There's no downside to picking up these cards basically, as they function just like a normal eShop points card would, just with a few extras in tow.
As of right now you can grab the cards at Target, and they can be combined for special scenes. Check out some pictures of the AR cards in the gallery below, as well as a handy QR link to download the photo app.