The guys of Gaming Boulevard wrote a piece about Nintendo Badge Center:
Nintendo Badge Arcade is a fun ‘game’ that’s free-to-play and free to download from the eShop right now. Since it’s free and you’re never forced to pay for a thing, we recommend every Nintendo 3DS owner to try it at least once. It offers fun badges as decoration of your home menu or self-created folders. Some of the badges can even replace the boring default icons. It’s fun to customize your Nintendo 3DS but beware of the price, spending a lot of money to collect virtual badges might not be the best idea ever. If you’re smart enough to play on the practice arcade and spent your money wisely, we’re sure you’ll have a blast with it!