Armed with the same impressive library of licensed artwork and faces found on its iPod and iPhone stickers, MusicSkins is now offering Skins for iPad ($20), interesting options that differ from ones we previously saw from GelaSkins. Here, the artistic sticker is solely for the iPad's back, while a completely clear screen protector is included for the iPad's face, unlike GelaSkins offerings, which leave most of the screen unshielded while providing…