Look forward to the demo.
Don't know if your engine supports it, but one trick that works for the background is to set the material to 100% emissive on your skycube. Right click on the material in AC3D, then move the emissive sliders until its completely white. This will help keep the walls of the cube from being visible. Make sure your set ambient and diffuse to black as well, it will keep the cube from getting over-saturated.
Also, again, don't know if your engine supports it, another tip is to turn z-buffer writes *off* when you render the sky cube. This will make it seem like it is an infinite distance, even if it is much smaller. (This part you can't do in AC3D, but its helpful once you finally get your model in your game engine.)