To make things interesting when you're in landscape mode the screen is 480 x 320 and effectively 640 x 320 with the scrolling thing, so if your wallpaper is 480 tall you'll lose 160 pixels, 80 from the top and 80 from the bottom.
This makes creating good Android wallpapers hard.
After some looking around I was about to create my own template when I found one on a forum. Very sorry, I lost the link, but I think this is the original from this author. If I am incorrect, let me know and I'll fix it.
This is a scaled version, click to open the original off picasaweb to get the template at correct size.