This video discusses creating a Texture Atlas for Sprite Kit. If you are familiar with sprite sheets for optimizing game graphics, a texture atlas is exactly that. You can name a folder with .atlas extension and include your standard and retina images (with @2x.png extensions). This .atlas folder with get packaged as a texture atlas at compile time. (Code to use the atlas is discussed later).
Watch these videos in order at Sprite Kit Tutorials with iOS 7 and Xcode 5
Find out more about all CartoonSmart's Sprite Kit Tutorials (and get the source files) at... cartoonsmartcode.com/sprite_kit_video_tutorials.php5