AntiCrop is a really useful tool for uncropping your images. So if you copped that image just a little to tight when you snapped the shutter just fire up AntiCrop. It allows you to add areas back into your image with auto fill. Works great at filling in small to medium amounts of space. You can also rotate and fill areas as well.
Get it at the App Store: https://itunes.apple.com/us/app/anticrop/id492663935?mt=8
Creators website with tutorials: http://www.handyphotolab.com