I'm doing the 3D tutorial and was trying to redo my fish animation in a similar '3D' fashion. I found myself thinking it would be cool to either drag a '3D' cube shape so that I can more easily position 4 'walls' and the sky and ground and then I could go in and edit or draw stuff in relation to this. A simple setup that places six vector planes in a cube and allows you to set the scale or resize would be great as lining up these planes manually is hard.
When I said a skybox I was referring to the way certain 3D programs allow you to select six equal sized images and generate a cube. This way I could draw 6 vector images, 4 of the horizon, 1 sky and 1 ground and click 'make cube' and then poof instant 3D vector cube then go in and add my trees etc instead of dragging and trying to get them lined up correctly.