UC500.com Cisco CallManager Express, UC500 reference

To modify the default backlight behavior for Cisco IP Phones under telephone service use the service phone command in telephony-service. While some service phone commands can be placed in an ephone-template, the backlight settings can only be done under telephony-service.

Guidelines

The service phone command in telephony-service configuration mode modifies vendorConfig parameters in configuration file for phones in a Cisco Unified CME system.

The vendorConfig section of a configuration file is read by a phone's firmware when that Cisco Unified IP phone is booted. The number and type of parameters may vary from one firmware version to the next.
The Paramaters are CASE SENSITIVE!!

The IP phone that downloads the configuration file will implement only those parameters that it can support and ignore configured parameters that it cannot implement. For example, a Cisco IP phone without a backlit display cannot implement backlight parameters regardless of how they are configured.

In Cisco Unified CME 4.0 and later versions, support for creating configuration files at a phone level was added for SCCP phones. This command in ephone-template configuration mode creates an template of vendorConfig parameters that can be applied to individual SCCP phones in Cisco Unified CME. This command in ephone-template configuration mode does not work for all vendorConfig parameters. 
if you use an ephone template to apply this command to one or more phones, you must also configure the cnf-file perphone command so that a separate configuration file is created for each phone, by MAC address. To apply this command in telephony-service mode to all phones of a particular type in Cisco Unified CME 4.0 and later versions, you can configure the cnf-file perphonetype command to specify that configuration files are generated by phone type.

To apply this command in telephony-service configuration mode to all phones in your Cisco Unified CME system, ensure that the system is configured for the default single per-system configuration file for all phones.

One of the default behaviors that I hate is that if the backlight is idle and a new call comes in the phone does not light up. To fix this do the below example.

Router(config)# telephony-service
Router(config-telephony)# service phone displayOnWhenIncomingCall 1

The following example shows how to set the default values for backlighting the phone display for all
Cisco Unified IP phones with backlight capabilities in Cisco Unified CME:

Router(config)# telephony-service
Router(config-telephony)# service phone daysBacklightNotActive 1,7
Router(config-telephony)# service phone backlightOnTime 07:30
Router(config-telephony)# service phone backlightOnDuration 10:00
Router(config-telephony)# service phone backlightIdleTimeout 01:00
Router(config-telephony)# create cnf-files
Router(config-telephony)# reset all

The following example shows how to set the backlighting parameters so that there is no backlighting of the phone display for all Cisco Unified IP phones with backlight capabilities until there is user interaction with the phone. The backlightIdleTimeout parameter is configured so that the backlight will switch off again after 60 seconds of inactivity.

Router(config)# telephony-service
Router(config-telephony)# service phone daysBacklightNotActive 1,2,3,4,5,6,7
Router(config-telephony)# service phone backlightOnTime 07:30
Router(config-telephony)# service phone backlightOnDuration 10:00
Router(config-telephony)# service phone backlightIdleTimeout 00.01
Router(config-telephony)# create cnf-files
Router(config-telephony)# reset all

The following example shows how to set the display parameters so that the phone display for all Cisco Unified IP phones with luminous displays are blank on Sunday (1), Monday (2), and Saturday (7):

Router(config)# telephony-service
Router(config-telephony)# service phone daysDisplayNotActive 1,2,7
Router(config-telephony)# create cnf-files
Router(config-telephony)# reset all