I'm trying to create a child theme of Twenty Ten that will allow users to select from a bunch of predefined header images, but which will not let them upload any of their own. I have already implemented the necessary functions to remove the default Twenty Ten header images and list my header images. What I have not been able to figure out is how to remove the section of the custom header page allowing users to upload their own image. I know that this page is generated by a core file so editing that is not an option. In looking at the code for how the custom header page is generated I did not see anything as simple as a hook or action for the user upload that would allow me to disable it. It also doesn't look as though the page is structured in a way that the user upload section could be hidden through CSS. Any help would be greatly appreciated.