I just installed the repsonsive background images module.
1. Do I need to create sized image styles and assign to individual breakpoint accordingly? like on the picture. https://drupal.org/files/project-images/responsivebackground.png
2. I uploaded a background image (1600px x 1200px) and I noticed that only the 320px breakpoint configuration works, the others make no effects. I don't know if it is something to do with my theme. I use the Omega4 subtheme.