iPhone 5 Wallpaper Alignment

I've tried setting an image as my wallpaper but it is a bit too short for the screen - it automatically aligns to the bottom so that the top has a black strip across the top. Is there any way of setting my iPhone to align the wallpaper from the top rather than the bottom? Or will I just need to adjust/choose another image? I've tried zooming in but it just distorts the image.