There is a method to remove the shadow gradient entirely if you have access to the device's file system.
1. Go through the file system on the device and navigate to /System/Library/PrivateFrameworks/SpringboardFoundation.framework
2. Look for "wallpaper-gradient-top-black-568h@2x~iphone.png" and "wallpaper-gradient-bottom-black-568h@2x~iphone.png"
3. Rename (preferably) or delete the image files as needed, if you're only trying to remove the top gradient then changing the "top" file will be enough
Doing this will also remove the shading in your lock screen, making the clock much less readable if you're using a bright background. This is easily remedied by going through photoshop and adding the "neutral density" gradient onto the background image.
Source:
http://www.reddit.com/r/jailbreak/c...weak_to_remove_the_wallpaper_gradient/cfs8sac