No kidding either, there are absolutely tons listed in this fantastic article by Nintendo Gamer. You’ve got characters from video games, comics, films and TV shows alongside real world celebrities and a whole bunch of others, so if you want to fill up your Mii Plaza with a bunch of new Miis, start scanning!
Here’s a sample to start off with:
And the full list can be found here:
Have to admit the choices here might be a bit questionable though. You’ve got Midna but no Princess Zelda? Bowser and Baby Mario but no normal Mario or Luigi? Mr Burns but no Homer Simpson? Oh well, they’re all free to use anyway, so it’s not like there’s too much to complain about here.
So yeah, there you have it, about a 100 Mii QR codes that work for both the 3DS and Wii U. Hope some people find them useful!