1. First find the image you want to replace your Extended Network space.
2. Resize the image to 435x75.
3. Upload your picture to tinypic.com or photobucket.com
4. Paste URL where it says URL HERE
5. Paste code anywhere in your edit profile section.
<style type="text/css">
table table table td {vertical-align:top ! important;}
span.blacktext12 {
background-color:transparent;
background-image:url('URL HERE ');
background-position:center center;
font-size:0px; letter-spacing:-0.5px;
width:435px; height:75px; display:block; }
span.blacktext12 img {display:none;}
</style>
(Credits to BBZ)