I’ve got a tiny cheap computer from Alix that I’m trying to set up as a digital display. The trick was getting it to open Chrome on startup, and setting the screen resolution correctly on widescreen TVs that apparently don’t report their preferred resolutions like monitors do.
Here’s a script to open Chrome:
rm -rf /home/display/.chromium-temp/* chromium-browser --no-first-run --user-data-dir=/home/display/.chromium-temp --kiosk http://YOURDOMAIN/sign
And to set the resolution to 1280×720 (might not work for you, might not be the right resolution. Check out xrandr docs and Google for using xrandr and related commands.
xrandr --newmode 1280x720_60 74.5 1280 1336 1472 1664 720 721 724 746 xrandr --addmode default 1280x720_60 xrandr --output default --mode 1280x720_60
Set these scripts to run on startup by creating a script under ~/.config/autostart (in Lubuntu/LXDE, search for the autostart script locations in your shell) pointing to these scripts. Make sure you chmod +x these scripts so they can actually run.