Your link had a typo. It's actually
http://www.cagesbydesign.com, but I agree with you: their background prints are really attractve.
The one reason I've always liked using plain white baclgrounds (and floors), apart from the obvious cost saving, is because white reflects light better, so it tends to disperse the light around the cage more fully which helps the plants lower down to grow a bit better, and make the cage a bit brighter for viewing.