Just boot up the computer in your secret base, and scan those QR Codes ! (Watch out, the camera is really sensible as hell!)
Here you go:
(Okay, I've heard this one is made for levelling up your Pokés, though)
This one's tough to scan, but it's a really special one. Can't read Japanese?
Okay. Let me tell you: it's Junichi Masuda's Base. To access it, go to Mossdeep City, and enter that door with nothing behind it once you have scanned the code
This picture is enough to tell whose base it is.
And finally, a Google Docs featuring (time when posted) 68 QR Codes:
Reminder: Bases also offers nice bonuses, like faster breeding, EV Training/Leveling, and more, depending on the Secret Pals you invite!
Also, keep collecting flags to get rewarded a Garchompite (Should be 50 or 100) !
A few Secret Bases for Pokémon OR/AS
A bunch of them, and a really special one is included.