The other day, I came across a site that created header graphics for those using WordPress on their own hosted file server. It is SUPER easy. In three short steps you can get your graphic.
First, upload a picture from your computer. Second, select which area of the picture you want made into the graphic (center, top left, bottom right), and, third, click create.
After the header is created, you can edit, save, start over, e-mail, share, or post to Flickr. If you save it, just upload it to your file server, and change your code to point to the header.
Here is the URL of the site: http://bighugelabs.com/flickr/blogheader.php
Try it out and see just how easy it is!!!
Here are 3 headers that I made in less than one minute.