With the BrightSign device, it is possible to use HDMI CEC to turn the screen on and off using the screen control settings in Signagelive. This is supported on all BrightSign devices, but you may need to enable it on your display. The option for this is likely in the settings page, and CEC has a range of brand names, some of which are provided below:
AOC: E-link
Hitachi: HDMI-CEC
LG: SimpLink
Mitsubishi: NetCommand for HDMI
Onkyo: RIHD (Remote Interactive over HDMI)
Panasonic: HDAVI Control, EZ-Sync, or VIERA Link
Philips: EasyLink
Pioneer: Kuro Link
Runco International: RuncoLink
Samsung: Anynet+
Sharp: Aquos Link
Sony: BRAVIA Sync
Toshiba: CE-Link or Regza Link
Vizio: CEC