cocos2d doesn't use @2x naming scheme. Instead it uses suffix -hd for iphone retina images, -ipad for ipad images, -ipadhd for ipad retina images.
Example: "Square.png" and "Square-hd.png"
You can also enable fallback suffixes. When enabled it will try to search for the following suffixes in the following order until one is found:
- On iPad HD : iPad HD, iPad, iPhone HD, Resources without resolution
- On iPad : iPad, iPhone HD, Resources without resolution
- On iPhone HD: iPhone HD, Resources without resolution
- On Mac HD : Mac HD, Mac, Resources without resolution
- On Mac : Mac, Resources without resolution
(as documented in CCFileUtils.h file)