The green iguana habitat can be as simple or as elaborate as you choose to make it. As long as the key elements, space, light, heat, and security are taken into account, you can make it an expession of your own creativity.
Space is important.
Make sure that one dimension is at least twice as long as your iguana, as measured from head to tail. It's better to start off with an oversized terrarium than to have to change it every six months. Lighing is critical to your green iguanas health. It requires a source of UVB light to properly metabolize calcium. Without this, it will develop bone disease and eventually die.