Adding PNG IMage to Twitter Bootstrap header

I've recently used Twitter Boostrap has a base for my design for my web application.  Unfortunately, as with any framework including CSS, it comes with a learning curve.  I have been tasked with adding a background image to the bootstrap header but unfortunately, it does not stretch enough to cover the header.  So for the nav header section, if I were to add the following code:

.navbar.navbar-inverse.navbar-fixed-top{
    background-color:black;
    position:static;
    height:100px;
    

}

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the header appears fine.  But if I were to add the following code:

.navbar.navbar-inverse.navbar-fixed-top{
    background-image:
    position:static;
    height:100px;   
}

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it doesn't look good.  The png image doesn't stretch to be the full height of the header.  How do I fix this?  Thanks!