Simple way to display pics on a monitor

I’ve been racking my brain over this seemingly trivial task the last several days. I have a monitor out in our waiting area that I would like to display full screen images (think advertising or instructions) depending on an automation task. I’ve been through google cast (no way to control screen saver/time out settings), lovelace casting (no easy way for full screen image displayed without menus, etc.) and finally using screenly on a raspberry pi (can’t get the custom screenly add-on to work). This shouldn’t be this difficult.