Mahjong (2013, Windows)
This game has unused graphics.
It's a bog-standard Mahjong solitaire game.
Unused Background Image
The game lets you choose one of twenty-two backgrounds to use as you play, but a twenty-third background named BGWood.png exists in the game files. If you choose the 'Wood' background option, the game uses a different (and much uglier) one instead of this.