Tue Dec 24, 2019 10:35 am
What you want to do is entirely possible. The standard Raspbian distro will work; it's the application which functions as a picture frame which is more important than the OS. Though a 'Runs in RAM' OS may be more appropriate if the Pi picture frame is likely to have its power-pulled rather than properly shutdown. Something like Ultibo or other Bare Metal will get the fastest start-up times but they might not support Wi-Fi.
I have used old TV's and Monitors as large digital clocks and that was just a few lines of Python code. I am sure such code could be extended to use digital photos pulled from a NAS, with transitions, scaling, rotation and other effects. But one of the digital picture frame projects already undertaken for the Pi would save you from doing any major work yourself.
First place to start would be a forum and Google search, find out what's already been done, and see if anything is suitable. Most guides will have something amounting to a step-by-step guide which tells you what you need to do.