Decrease Spacing Before Header Picture

That space is being created by this:

#page {
    margin: 2em auto;
    max-width: 1000px;
}

Change the 2em. But I see that you have a child theme — with the entire twentyeleven stylesheet in it – not the ideal way to set up a child theme. So find it in there.

For working with CSS, try using Firebug — which will show you exactly which CSS is affecting a specific area/element of the page.