@Zampa
Painting the ceiling (4th wall!) is a great idea. We've just painted ours and it makes the room come together.
Don't knock it until you've tried it!
Do your rooms not already have 4 walls?
I actually really like their blue rooms and the blue ceilings. I'm not sure I could live with both together, but I imagine of you did just the ceiling and not the walls it would look odd? Is your ceiling the same colour as your walls?
The white/silver one is terrible though. The kitchen is the worst. The gym/sofa room is confusing. Do you think they work out whilst other people lounge on the sofa and watch them?