The PhaserGames.com site has a new tutorial series on creating an Endless Runner game in Phaser. In part six: "Whenever we decide to develop a game in the office, I usually want to get started on it right away. Of course, the artists need time to develop the artwork. In the meantime, I use temporary graphics or what one of my artist friends calls “Dev Art”. I also sometimes use this on a game I’m developing which I’m not sure will be released, and don’t want to put a lot of time in before I’m sure."