Once you have beaten both the R-1 mode (including Mewtwo) and the R-2 Mode (including Mewtwo), you are given a set of bonus stickers that you can access in the Gallery Mode. When you're on the Gallery main screen, press and hold L and R and move the Cursor to Print. If you keep the buttons pressed, the Print option will now change to Bonus. You will now have access to a set of 16 bonus "wallpaper" stickers from all the different modes that you can print out at "Snap" Stations.