Apple's wallpaper adjustments for iOS leave something to be desired. You can't rotate the image, and if you try to scale it, the image often snaps back, making a mess of your intentions.
Fix and Set Wallpaper (U.S. $0.99) is a simple app that fixes Apple's shortcomings. You can pinch, rotate, crop and position a photo however you want. You can preview the wallpaper on your home screen. If you use a photo zoomed out, the app adds a black border to your image. When done, you can save the photo to your library, then set it as wallpaper using Apple's tool. There is also an option to share your new wallpaper via email or iMessage.
Fix and Set Wallpaper for iOS
The app let me use some photos as wallpaper that just couldn't be sized properly before. I do wish the app wasn't so basic, however. When you launch it, there are no instructions. You load an image, and then it stares back at you. Of course you can rotate, reduce and enlarge it with gestures, but it isn't really explained. There are three cryptic dots at the bottom-right corner of the screen. They allow you to see the app controls, but it is a strange icon to use for that purpose. Skitch is also minimalist, but it explains the interface before you use it.
I'd also like to see the app add some filtering and image-adjustment tools. I know I can do that in other apps, and then load the altered photo as a wallpaper, but it would be nice to see it all built in here.
Fix and Set Wallpaper overcomes Apple's limited wallpaper feature set, and is certainly worth the asking price. It's highly rated at the app store and I concur that it does the job.
The app requires iOS 7 or later, and it is optimized for the iPhone 5.