This is a tool that, when run, will download and decrypt and extract the PNGs for every badge in Nintendo's Badge Arcade.
Note: Decryption requires you to be running a copy of 3DS Crypto Server on a 3ds on your local network, and for you to edit the TryDecryptBOSS function in NetworkUtils.cs to point at that 3ds. Decryption cannot avoid networking through a 3DS without the BOSS key from bootrom, which has not been publically dumped.
The first time this is run, it will generate a ~3 MB log file as it extracts every badge ever added to the arcade.
On future runs, it will only download/decrypt if there are new badges you haven't already downloaded, and will only log the new ones.
Source is available on my github.
Note: This tool has a lot of setup requirements, and as such it's only really reasonable to expect devs to be able to make use of it.