How to I get my header to scale when rotated to landscape? Right now it looks great in portrait but as soon as it is rotated it just shows the header image centered with white spaces on either side. I've tried changing the width size but it doesn't work. What am I missing?

Good question, and one I would like to know the answer to as well!

This is always a tough one to figure out. The header image (for small and large devices) is tough to get right because the image may or may not 'look right' in both orientations. The design is also important to consider....the best design depends on the nature of the graphic. Example: A company logo should probably remain scaled and centered but a landscape type image, like a banner or someting maybe not. I've found the best way to do this is to design the artwork in such a way that is balanced nicely with the background color, or image. Getting the background and header image to compliment each other isn't easy. Not sure how to best advise...the app won't magically scale the header image, it's going to be centered in both orientations. You could prevent the rotation, get it to work well with a the background art, omit the header all together and use a background only...lots of ways to do this. You'll have to decide the best approach.