The background is inside the tank.
Juwel make structured backgrounds in a variety of styles e.g. clay, stone, granite, tree roots. They have to be siliconed in, but it was easy enough to do. You can check out the backgrounds here: http://www.juwel-aquarium.de/en/motive_background_stone494.htm
I think they are a bit of a rip off, as for my tank I needed to buy two, and as you can see in the picture I only used a really small piece for the second bit. But in saying that I'm really happy with how it looks. And it should look even better once the plants grow around it.
My only concern is if it becomes dirty how I'm going to keep it clean as its polystyrene , though from surfing the various forums around the world people don't seem to have that issue with them, though time will tell I guess.
The sand for anyone that is interested is 1-2mm grade Basalt rock.