Enduro.js has spritesheet generation built-in.
Save all your sprites to assets/spriteicons. These sprites should be png and you also need to save a double sized sprite, with @2x added at the end of the name.
The spritesheet generation process will generate a .scss file that stores coordinates for each sprite. You have to include this file in your main.scss file. Use syntax below to include this file.
You can access the sprites with a convenient mixin
@include retina-sprite($<original_file_name>);. This mixin will set the background image, its position and its size.
Credits to https://github.com/Ensighten/spritesmith, which enduro.js uses internally to provide support for retina sprites.