Header/Coding help?

[aprilraven]

Hi, I'm trying to replace my journal header with a different banner but I'm not sure what I'm doing. A friend originally set up my LJ for me ages ago, I think they were working with custom external stylesheets. I can see the code they used, but there seem to be some things missing just from what I've browsed here at your journal. What I'm trying to do is add this new banner: http://ic.pics.livejournal.com/aprilraven/16525607/142704/142704_600.jpg

I know where to put it in (in the code below) and it shows up, but I'm trying to get it to stretch out just a little more and can't quite figure that part out. Any help you can give me would be greatly appreciated. My LJ is a paid account: http://aprilraven.livejournal.com/ The link for how to post coding here wasn't working, hope it's ok for me to plug it here like this.

.headerimage {
height: 550px;
background-image: url(" http://i793.photobucket.com/albums/yy217/tf_epic_recs/AR.jpg") !important;
background-repeat: no-repeat !important;
background-attachment: scroll !important;
background-position: center !important;

margin-bottom: 15px;
}

.b-repost-item, FORM#qrform > TABLE[style="border: 1px solid black;"]:last-child TD[style="vertical-align: top; text-align: right;"]:first-child { display: none !important; }