Question : Customizing the back of an iPad (silk screen? sticker?)

I need to customize the back of an iPad with a graphic. My question is: What is the best way to do this? Namely:

1. Are there companies that will silk screen directly onto the iPad (or will that void the warranty?)

2. If the best way to go is something you have to peel off and apply, what's the best company to go with/easiest product to apply?

(I'm based in LA, so if there are any companies you know of that will apply it on-location, that'd work too.)

Thanks!

Answer : Customizing the back of an iPad (silk screen? sticker?)

These guys are good and inexpensive.
http://www.uniqueskins.com/Products/Apple/Custom+Apple+iPad+Skin