Fantasy/sci-fi artist Lee Macleod has updated his personal website with some relatively high resolution versions of the cover artwork he created for Sir-tech's Wizardry Gold, the NES version of Ultima IV: Quest of the Avatar, the SNES version of Ultima VI: The False Prophet, and several other games. The Ultima VI artwork is by far my favorite, as it features the avatar, a gargoyle, a moongate, and a far-off castle in the same scene. It'll be somewhat pixelated to use any of it as wallpaper on a PC, but it'd certainly work great for portable devices.