Adjustment to boxed content area.

I am working with the velvet theme (esp because of video capability) which is great but would like to make an adjustment to the background content box. I am using ‘boxed content’ in order to have background image but I would like to get the boxed content area to read as two boxes rather than one (akin to Twicet homepage) such that there is an upper box that would combine header and slideshow and a lower box that would contain other content and footer. I want to beable to read the background image in the gap between the upper and lower box…Perhaps a clearer way to express this is to make boxed content area transparent and add background to smalled content boxes. Any help would be much appreciated. I am new to this – so I may not be expressing this properly. I am working on a local host and so development work is not online but I could email you a screen grab to illustrate. I would also like to use the twiset menu format – so that the submenu is revealed through drop down menu