Reader LMP showed how you can view all of an application’s graphical resources—its icons, pictures, UI (user interface) elements, and so on—quickly and easily by dragging the application icon onto the Preview icon. When you do this, Preview’s sidebar will show all of these items, and you can click on any one to view it in the main window.
With Keynote, for example, you’ll gain access to all the graphical elements in the various themes the program contains; and with Pages, you’ll be able to see all the elements from the program’s templates. These latter programs’ contain thousands of graphics, so it may take you a while to wade through them all. But you might find something interesting.