Absolutely.
I created my top banner/nav bar with fireworks3
Then I exported it using slices and creating the dreamweaver htm.
Copy/paste the code from dreamweaver into the "Header" box in the admin CP (putting it in the right spot was the part that took a couply tries). You will have to edit the forum links by hand.
You can see the header here
http://www.duboisi.com
Was actually pretty easy, but make sure you back things up.
Kevin.