Modifying Pages Dashboard Options/Functionality

Hey,

Does anyone know of the appropriate functions/approach to target if I want to modify the layout and functionality of the default pages menu? (Dashboard > Pages > Click on a page to edit) I’m talking about the ‘Click on a page to edit’ part.

I want to clean up the custom fields option by adding functionality so that a user can click browse to upload an image, and that image will then be used for the sub-header of the respective page.

I know how to create theme options,but what I am not sure is how to target the changes on the actual page view when accessed via Dashboard > Pages > Page Name.

Thanks!