Background module position was prepared especially for a 2 modules, "slider module" and "background image module". It allows to add different background images or images slider to the background of template.
Template is based on Bootstrap grid layout (12 columns - Fluid Width Layout).
Template contain mix of two types of module positions, standard module positions and flexible module positions which are additionally controlled by template.
Standard module positions available in template:
main-sidebar-top, main-sidebar-middle, main-sidebar-bottom, background, above-mobile-menu, below-mobile-menu, menu, breadcrumbs, footer, disclaimer, debug.
Flexible module positions available in template:
top-a, top-b, maintop-a, maintop-b, mainbottom-a, mainbottom-b, bottom-a, bottom-b, sidebar-left, sidebar-right.
By default, all modules published in these positions are displayed in columns and grouped in rows, up to 4 modules per row. All modules in row will have an equal widths. Additionally, you can switched desired flexible module position to "custom widths", to use custom alternative layout for modules. You can set manually width of every single module. With custom widths option selected you can publish up to 12 modules in a single position, all modules are displayed in a single row.
This option utilizes native function introduced in Joomla 3, named "Bootstrap Size" and it can be found in advanced settings of every module.