Steve wants to use TV screens to create a large screen photo gallery in his home. Leo says he could use a Chromecast or Apple TV for each TV screen and stream photos from Google Photos. He would also want to join all screens together for one big picture. Leo says that could be a bigger challenge because each TV has to join with the other. A Raspberry Pi could perhaps do it, but you'd have to write custom code to be able to create a Video Wall Mosaic. There are video wall controllers out there. They aren't hugely expensive either. About $200-300 or more. They are programmable too. Samsung makes one.
Here's another idea .... https://piwall.co.uk/information/10-create-your-own-gpl-movie-piwall