There are a number of ways to make a TV screen usable as digital signage for your church:
A little device called the Raspberry Pi paired with display software or a kiosk app; examples from binary emotions: http://www.binaryemotions.com/. Also with Raspberry Pi, you can load Microsoft 10 Internet of Things (IoT) OS to provide a kiosk app. Or, you can use screenly.io for more robust tools. YouTube Tutorial Video
Something called the Micca Speck G2, a tiny media player http://www.miccatron.com/micca-speck/
Some TVs can just load and loop content off a usb stick, but then you have to unload the stick to change content.
Wifi TV? Chromecast, Samsung AllShare Play, MiraCast, or Chrome Sign Builder.
Non Wifi TV? Check out the ViewSonic NMP-302w for a wireless connection to your PC with a centralized interface. Dynamic content including video streaming, web-based content, RSS feeds, etc and can be programmed on a schedule (i.e., show different things on Sundays than during the week).
For multiple screens and a customized professional solution, check out https://www.brightsign.biz/. Products range from $450 and up.