As @Mattliblove suggested, you can easily recover all kinds of files from iTunes or iCloud backup. Sadly, there are users who were not aware the importance of data backup. So in such case, they need a data recovery software to help them out.
Recuva from Piriform is a free data recovery utility and it's capable of restoring most of the deleted data from various storage media devices.
Step by Step Tutorial: How to recover deleted iphone photos
iPhone Data Recovery is another data recovery app designed for iPhone phone users. It enables you to restore deleted & lost contacts, text messages, call logs, notes, Calendars, reminders and Safari bookmarks from iPhone 6S/6S Plus/6/6 Plus/5S/5C/5/4S/4/3GS,iPad pro, iPad mini 4, iPad Air/Air 2, iPad mini 2/3 (Retina), iPad mini, iPad with Retina display, The new iPad, iPad 2/1, and iPod touch 5/4, etc. At the same time, you can use it to scan camera roll, photo stream, photo library, message attachments and voice memos that exist on your iOS device.