The skin you are using is nice (Vista Black).  The logo in that skin simply displays the image in the designated area (left side of the header area).  Based on what you said, I am not clear on what you are trying to accomplish.  As a guess, I am thinking you want the entire header area to have the same orange background as your logo?  If this is the case then you would most likely need to make some modifications to the skin files (.ascx) and associated CSS files.  Depending on level of expertise in XHTML/CSS and/or DNN, I would recommend looking at some skinning guides and tutorials to get a feel for what you want or can do.

Another option - though they charge for it - is to contact dnnskin.net (the makers of the Vista Black skin you are using) and get them to customize it to your specifications.

In either case it might help if you got a mock-up done in Photoshop or Paint.net to clearly show what you want the end result to look like.  Best of luck, cheers - Jeremy