Adjustment of the page header

[thedaimaofanficarchive]

Hello!

My name is Stefanie and I joined DW only very recently.

I have a question regarding the customizing of my header and I hope that some of the people in this community who are more familiar with CSS codes than I am can help me out.

I use the "Decadence" theme for my journal and I want to apply a header for it.
I want my header to be offset, meaning hiding the journal title and just show my image instead.
I used the following CSS code:

#title span { display: none; }
#title {
width: 1000px;
height: 503px;
background-image: url(http://i1382.photobucket.com/albums/ah260/celtic_rose/1039851_478430295566280_996037395_o_zpsqolbonoi.jpg);
background-repeat: none;
}

And the result I got is the following:



I'm happy with the size of my header, however, I would like it to either stretch all the way to the right of the top page OR to be in the top center of it.
How do I need to change my CSS code in order to achieve that?

If someone could help me out and provide me with adjustments to my CSS code for
option 1: header spreading over the whole top page
option 2: header as it is now, but in the center of the top page
it would be really appreciated.
Thanks!