In Germany you can buy the Point of View Mobii 731N-Tablet for 33 Euro. This is cheaper than any other external display or an used Samsung SPF-Photoframe on eBay.
I bought one of these PoV-Tablets, installed Full Screen Browser and full!screen and did a quick & dirty configuration with the template from this thread (it's not perfect, but in the moment for testing it's good enough).
Works like a charme: