LG Vortex Question

[LoveMyDroid02]

Hi, I have a friend that has a LG Vortex and has a screen res of 320x480, so I was wondering if someone could tell me what size the wallpaper has to be in order to display proper. Like I have the droid 2 which the screen is 854x480 but the wallpaper size has to be 960x854 to display without making the image look crappy. If someone could please help I would appreciate it. Thanks!