I don't know if the contest is open world wide, but still i want to participate!!
Since this tiny machines are mainly thought as multimedia centers, the box design should be decorative, to be able to use it with a big plasma Tv (wich for argentine are very epensive, but not for US).
I also thought of having the power conection hidden, as to be used with wireless elctricity (http://el-blog-de-mau.blogspot.com/2009/07/lo-que-estabamos-esperando-electricidad.html).
The last IDEA is that it will need space for a dual webcam and microphone (similar to microsoft proyect natal) to low body motion control.