I understand better now, what you want to do. In the Tk widgets demo, there is an example called "tiles and transparent images". That should give you a start.

You are probably really pushing the limits of what the ordinary Canvas can do, if you start moving things around, and expect the transparency to update itself without distortions. I would switch to Zinc. It has better 'group' support and many other improvements over Canvas, that would make your job easier.

And forget the second canvas idea. You won't be able to see thru it, without faking it, by taking what is currently below it, and mirroring it above. You can check out Zinc - Star Wars Scrolling Text for an idea of what Zinc can do, you can add images to the background(or scroll) if you wanted, or make everything draggable.