I have large icons I wanted to display in the header so I increased the height of the header. However instead of growing the header it replicated it so I get a really funny look: The icon is 48x48 (shows up in VS just not on the dev deployment where I took the screenshot).
That happens because background images are used and they are not high enough, so they are repeated by browser. You may create custom images with large height, set them to custom css classes and assign those classes to the "HeaderXxx" properties of RoundedCorners.