Facebook released an update to its iOS app this week. Included in the change log was group-messaging enhancements, along with adding the ability for users to change their cover photos.
The feature was once in the Facebook iOS app, but was removed when Facebook released the completely native, revamped iOS app. Android users received a similar native update, and shortly after its release the ability to change cover photos was added.
After you update to the latest version of Facebook, launch the app and navigate to your own Timeline. Once there, tap on your cover photo.
You'll be able to pick a photo from your photo library, take a photo, or view your current cover photo.
In some instances you can move the photo around and adjust it to fit just right, but I was only able to adjust one or two photos when trying to change my cover photo using the app. The rest of the photos, which are larger than the cover photo size, were placed for me and didn't allow for any adjusting. Your experience may vary.