Digital signage with non local access & preferably auto update via a file manager/email/ Gdrive

Hey, I have been tasked with sorting a digital sign for sponsors. Having used Pi's several times, I know you can do this with them, however I have a few caveats. Use case: Digital Signage Use load: 4 images maximum or a mp4 of said images with controlled transitions. Set up: The pi will be permanently to a TV/ digital projector to loop the images/video. Access: I want this all to be done, preferably, from the comfort of my own home & for free/ no subscription or one off payments to a software. I'd love to have it so that I can upload to a file manager online ie google drive and the pi just reboot and pull the images each time it detects a change in said file system. Or if I email it across the the pi, each email same again. Reboot, pull the new files. Personal Thoughts:: I've been googling around for two daysIsh and found, but I don't think that can be access off site. Also saw Slidesho for Android, which could work if I loaded Android onto a Pi. Any thoughts/ help would be warmly welcome. Thanks

I think Pisignage is that play actually.

Now I'm back thinking it's Screenly actually.