Yealink T58A Administrator's Manual page 61

Permitted
0-System, the LCD screen will display the built-in picture.
Values
4-Custom, the LCD screen will display the custom screen saver images (configured
by the parameter "screensaver.upload_url"). If multiple images are uploaded, the
device will display all images alternately every 60 seconds.
Default
Blank
Web UI Settings > Preference > Screensaver Type
Phone UI
> Settings > Device Settings > Display > Screen Saver Type
For Common Area Phones:
(default password: admin) > Screen Saver Type
Parameter screensaver.upload_url
Description
It configures the access URL of the custom screensaver background.
Permitted URL within 511 characters
Values
Default
Blank
Web UI Settings > Preference > Screensaver > Screensaver Type(Custom) > Upload
Screensaver
Parameter screensaver.background
Description
It configures the background for the screen saver.
Permitted
Default.jpg
Values
01.png
02.png
03.png
04.png
05.png
06.png
07.png
08.png
Default
Default.jpg
Web UI Settings > Preference > Screensaver > Screensaver Type(System) >
Screensaver Background
Settings > Preference > Screensaver > Screensaver Type(Custom) >
Screensaver
> Settings > Device Settings > Screen Saver
| Device Customization | 61
<y0000000000xx>.cfg
<y0000000000xx>.cfg