I did something like this, firstly using Python, Qt and Mono on Acer Revo Aspire One machines running Ubuntu, and indeed this is something I want to do on the Pi too.
I had a small Mono (C#) program that would connect to a file server on the network (or later, an FTP server across the web) and fetch down 'slides' (just full-screen jpgs). These would go into a folder on the Acer. Also running was a Python & Qt 'embedded browser' - just the standard Qt browser control with no navigation tools or key handling, set-up to launch itself full-screen and read the first slide in the folder. Each slide was effectively a .html page and a .jpg, and the point was that the meta tags in the html header could control which slide was going to be shown next and for how many seconds the current one would be displayed (etc). It was a mixture of technologies languages simply because it was a learning 'project' and we had a pile of these Acer machines and no Windows licenses.
I'm hoping to do something similar with the Pi, whether I write it all in Python or something else,.
One problem we did find was that sometimes the TV screen just wasn't very visible in the shop window, in sunlight. On the shops where this wasn't a problem the whole thing worked brilliantly but where the light was a problem it really could spoil the whole thing.
The last iteration of the software had the Mono code also fetching back database information from the remote server so we could display up-to-the-minute exchange rates etc and so I'm hoping to be able to achieve this on the Pi too, even if it's just a case of writing an ASP-type page on the server to get the rates and format them into a HTML page that can be statically downloaded and shown as if it was a slide, if you see what I mean.
Rob, Robsoft. Delphi, C#, SQL Server, Xamarin, Raspi