I built a Digital Signage solution using Kentico, it is just a webpage that has some javascript to do a continuous loop displaying content (it does a page reload after x number of loops). I use Kentico tree to manage the content for each "slide" of the page. I use GSAP to animate the content on the screen. Then just the browser running in Full Screen on the TV.
I am not sure about displaying a power point on a webpage, but I am sure there is some solution for it. You would probably have to create a custom page type to upload the file, but not sure how you would display that content. Probably some way on the backend to pull the data from each slide as an image or something.
As far as Flash, you might want to avoid something like that for displaying on a browser, since it's getting blocked by a lot of browsers, but you probably can do something to allow it.