For all players of Pokemon Diamond, Pearl, and Platinum - Provided you're NOT a cheater and DON'T have an Action Replay, I have something interesting for you. If you have an AR, you've probably done this already without the help I'm about to provide.
http://www.filb.de/games/tools/aikotoba
Go there, give it your game's Trainer ID and whatever version you're playing. After this, go to Jubilife's TV station and talk to a guy on the 3rd floor who will ask your input about TV. Depending on which wallpaper you want (you can keep doing this to get all of them,) you put in the 4 words (he'll ask for 2 at a time.)
Enjoy. Just a nice little thing that I THOUGHT only Japan had. I have no idea how we were supposed to find them through normal means.