How to extract Keynote template image background
I'm new to using Keynote, although I've used PowerPoint in the past. I've chosen a theme (Moroccan) for the presentation but not all of the master slides contain the blue background image. I'd like to modify the image slightly (removing a box) in Photoshop but for the life of me I can't figure out how to get at the actual graphic file. I've found a set of instructions for burrowing down through the folder and using Show Package Contents but the images in Mt. Lion are obviously in a different place than they were when the instructions were written.
Does anyone know where the full-size background images are hidden for the current version of Keynote?
MacBook Pro (17-inch Mid 2010), OS X Mountain Lion (10.8.2)