Layer is a service that allow easy integration a chat function to the App. I have been reading their document, and Atlas is a lightweight, flexible set of user interface components designed to enable developers to quickly and easily integrate native communications experiences into their applications. It was designed and built from the ground up to integrate with LayerKit the native iOS SDK for accessing the LayerKit communications platform.
Sending Image is basically automatically handle by Altas, but in order to view the image after receiving, you must set up autodownloadMIMETypes property for Layer Client.