It'd involve using masks, or at least layers. Make the giant J on one layer, put the background photo on the layer below it. Then select the J shape, invert the selection and delete that part from the background layer. Turn off the visibility on the J layer and you should have your J with the photo you want inside it.
I think that's what you meant anyway. Would suggest going to a graphics forum, someone there might do it for you (I would of but I'm not near the computer!).