I know very little about this plugin, please provide me with more details and I will try to help you out. One of the reasons why full background plugin might not work with this Theme is plugin not being "responsive".
I strive to make this Theme as simple as possible, but not all plugins are guaranteed to have full compatibility with the Theme :)
Side Note: if you're making any modifications to parent Theme (Responsive) itself, please use http://themeid.com/forum/topic/505/child-theme-example/ Child Themes are highly recommended even by WordPress. http://codex.wordpress.org/Child_Themes