I really don't. It make's the Tamagotchi look to confusing and makes more attention to how the Tamagotchi looks rather than the creature you are taking care of. Post how you decorate your tamagotchi!
I did that to my V3. Just use very non-sticky stickers so that they peel off easily. It is quite cute. My friend TamaGold did that as well! It is fun to decorate because it makes the Tamagotchi "yours" rather than just something that you have bought and hung around your neck. It's also like decorating your pet's enclosure - it makes it a nicer home for the Tama!