The only way I found of adding a custom wallpaper to an iPad leaves that wallpaper mixed with all the photos. Can I somehow specify that it's a wallpaper and should go into the list of wallpapers?
(couldn't find this by googling...)
I don't believe you can, maybe with jailbreaking?
However, after setting the wallpaper, you can remove it from your photo library without affecting your wallpaper selection. This may be a bit inconvenient when you regularly switch between wallpapers, but it is as close as it gets.