Splintering off from the discussion in another thread about artwork and alternate covers on the opposite side of game coverslips, here's a new topic for those. I have a now-outdated picture of all the PSP coverslips I have with inside art: 
Since that picture was taken, I've also gotten Ys: The Oath in Felghana, Ys I & II Chronicles, and The Legend of Heroes: Trails in the Sky, for a current total of 16 PSP covers with inside art. Publisher distribution: 5 from XSEED Games, 4 from Square Enix, 3 from Sony, 1 from Konami, 1 from Sega, 1 from Atlus, 1 from SNK Playmore.
Hatsune Miku: Project DIVA's inside artwork is kind of fun, in that the game manual, when in place, keeps the picture complete thanks to the art on its cover matching the top half of the coverslip's inside art.