If you're working with an IKEA Pax wardrobe system, for example, you need square mirror tiles for the Bergsbo and rectangular or square tiles (if you space them out right) for the Forsand.
BATTA!] over at IKEAhackers ran into this problem, and solved it by building a complete electronics workstation inside a wardrobe. The base of this project is a storage unit called PAX ...