Visitor selfies with augmented biorality

Good afternoon!
I need to implement the following functionality in an app:

  1. Visitor’s selfies with augmented bio-reality - it’s just a selfie that by random geolocation sometimes overlays the visitor’s photo on a background we made beforehand - for example, a photo of a frog or a beaver))) Or a beaver on the visitor))

Can you tell me how it can be done?