Auto stretch header

[steven s]

I don't see a way unless you change your image to have horizontal lines.
You could use a 3 column table with your image in the middle and continue with the background in the outside columns using the background tag.
But they would need to be horizontal lines that meet up with the center image.

Edit: Oh wait.
Do you want to use the image on your website now?
You could create a table and use the td background tag of just the background.
Or better yet, separate the background image and use that as a background tag. Set the table to 100%.