mesh_{size}_bg_size

If you are familiar with Foundation’s interchange functionality you know that interchange will swap out image (and other content) based on the viewer’s screen size.

You can use the following filters in conjunction with add_image_size to define the dimensinos for default, medium large and xlarge sizes.

add_filter( 'mesh_default_bg_size', $size );
add_filter( 'mesh_large_bg_size', $size );
add_filter( 'mesh_medium_bg_size', $size );
add_filter( 'mesh_xlarge_bg_size', $size );