Here's how I did it..
Sign into blogger.. go to 'layout' - 'edit html' -
Scroll down the 'Edit Template' window until you see the text in the screenshot below.. ( it's almost at the bottom)
Just Click on the screen shots to see them full size.. (this is a first for me.. Posting screenshots.. I do hope I get better at it..lol ..)
Now skip the middle 'showaddelement'.. and change the lower 'showaddelement' to 'yes'..
It will look like this;
Now click on 'Save Template'.. When you go to your blog layout - page elements - you will have a new gadget box for your header and your blog posts.. The gadget box above the header is where I added my new banner.. I added it as 'new gadget' - 'picture' - then just moved it below the header.. And I just love it !!
Hope this will be helpful to you.. And as always, just drop me a line if I can be of any help to you..