A free program for Android, by OT Apps.

Flag My Picture is an application that lets you easily change the images on your mobile device with the country flags. There are many different flags from all around the world, such as Afghanistan, Albania, Algeria, Australia, Austria, Azerbaijan, Belgium, Bangladesh, Belarus, Belgium, Bahamas, Bahrain, Brazil, Bulgaria, Burundi, Cambodia, Canada, Chile, China, Colombia, Costa Rica, Croatia, Czechia, Denmark, Dominica, Dominican Republic, Estonia, Ethiopia, Fiji, Finland, France, Germany, Greece, Guatemala, Guinea, Guinea-Bissau, Haiti, Hungary, Iceland, India, Indonesia, Iran, Iraq, Ireland, Israel, Italy, Jamaica, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia, Madagascar, Malaysia, Malta, Mauritania, Mexico, Mongolia, Morocco, Netherlands, New Zealand, Nicaragua, Nigeria, North Korea, Norway, Pakistan, Palau, Paraguay, Peru, Philippines, Poland, Portugal, Puerto Rico, Romania, Russia, Saudi Arabia, Singapore, Slovakia, Slovenia, South Africa, South Korea, Spain, Sweden, Switzerland, Taiwan, Thailand, Tunisia, Turkey, Uganda, United Arab Emirates, United Kingdom, United States, Uruguay, Uzbekistan, Vietnam, and Western Sahara.

You can use the app in the following ways:

Select a picture from your device’s gallery.