Tizen Developers

Did you just want to change the wallpaper of lock screen? If yes, I think the system_settings.h api can help you. Paste the relavant api below, for more detailed please search in help doc. Hope this can help you. ;)

/**
 * @brief Enumeration for System Settings Key.
 */
typedef enum
{
    SYSTEM_SETTINGS_KEY_INCOMING_CALL_RINGTONE, /**< (string) The file path of the current ringtone */
	SYSTEM_SETTINGS_KEY_WALLPAPER_HOME_SCREEN, /**< (string) The file path of the current home screen wallpaper */
	SYSTEM_SETTINGS_KEY_WALLPAPER_LOCK_SCREEN, /**< (string) The file path of the current lock screen wallpaper */
	SYSTEM_SETTINGS_KEY_FONT_SIZE, /**< (int) The current system font size */
	SYSTEM_SETTINGS_KEY_FONT_TYPE, /**< (string) The current system font type */
	SYSTEM_SETTINGS_KEY_MOTION_ACTIVATION, /**< (bool) Indicates whether the motion service is activated */
	SYSTEM_SETTINGS_KEY_EMAIL_ALERT_RINGTONE,  /**< (string) The file path of the current email alert ringtone */
	SYSTEM_SETTINGS_KEY_USB_DEBUGGING_ENABLED,  /**< (bool) Indicates whether the USB debugging is enabled */
	SYSTEM_SETTINGS_KEY_3G_DATA_NETWORK_ENABLED,  /**< (bool) Indicates whether the 3G data network is enabled */
	SYSTEM_SETTINGS_KEY_TAP_AND_HOLD_DELAY,  /**< (int) Indicates delaying time of 'tab and hold' (sec) */
	SYSTEM_SETTINGS_KEY_LOCKSCREEN_APP,  /**< (string) Indicates lockscreen app pkg name  */
	SYSTEM_SETTINGS_KEY_DEFAULT_FONT_TYPE,/**< (string) The current system default font type (only support Get) */

	SYSTEM_SETTINGS_KEY_LOCALE_COUNTRY,		/**< (string) Indicates the current country setting in the <LANGUAGE>_<REGION> syntax. The country setting is in the ISO 639-2 format, and the region setting is in the ISO 3166-1 alpha-2 format */
	SYSTEM_SETTINGS_KEY_LOCALE_LANGUAGE,	/**< (string) Indicates the current language setting in the <LANGUAGE>_<REGION> syntax. The language setting is in the ISO 639-2 format and the region setting is in the ISO 3166-1 alpha-2 format. */

	SYSTEM_SETTINGS_KEY_LOCALE_TIMEFORMAT_24HOUR,	/**< (bool) Indicates whether the 24-hour clock is used. If the value is @c false, the 12-hour clock is used. */
	SYSTEM_SETTINGS_KEY_LOCALE_TIMEZONE,	/**< (string) Indicates the current time zone. */
	SYSTEM_SETTINGS_KEY_TIME_CHANGED,		/**< (int) Indicates the current time zone. */

	SYSTEM_SETTINGS_KEY_SOUND_LOCK,					/**< GET (bool) Indicates whether the screen lock sound is enabled on the device. ex) LCD on/off sound */
	SYSTEM_SETTINGS_KEY_SOUND_SILENT_MODE,			/**< GET (bool) Indicates whether the device is in the silent mode. */
	SYSTEM_SETTINGS_KEY_SOUND_TOUCH,				/**< GET (bool) Indicates whether the screen touch sound is enabled on the device. */

	SYSTEM_SETTINGS_KEY_DISPLAY_SCREEN_ROTATION_AUTO, 	/**< GET (bool) Indicates whether rotation control is automatic.*/

	SYSTEM_SETTINGS_KEY_DEVICE_NAME, 					/**< GET (string) Indicates device name. */
	SYSTEM_SETTINGS_KEY_MOTION_ENABLED, 				/**< GET (bool) Indicates whether the device user has enabled the motion feature. */
	SYSTEM_SETTINGS_KEY_NETWORK_WIFI_NOTIFICATION, 		/**< GET (bool) Indicates whether Wi-Fi-related notifications are enabled on the device. */
	SYSTEM_SETTINGS_KEY_NETWORK_FLIGHT_MODE, 			/**< GET (bool) Indicates whether the device is in the flight mode. */

	SYSTEM_SETTINGS_KEY_SCREEN_BACKLIGHT_TIME, 			/**< (int) Indicates the backlight time (in seconds). The following values can be used: 15, 30, 60, 120, 300, and 600. */

	SYSTEM_SETTINGS_KEY_SOUND_NOTIFICATION, 			/**< (string) Indicates the file path of the current notification tone set by the user. */
	SYSTEM_SETTINGS_KEY_SOUND_NOTIFICATION_REPETITION_PERIOD, 	/**< (string) Indicates the time period for notification repetitions. */

} system_settings_key_e;

/**
 * @internal
 * @brief Sets the system settings value associated with the given key as a string.
 * @since_tizen 2.3
 * @privlevel platform
 * @privilege %http://tizen.org/privilege/systemsettings.admin
 * @remarks #SYSTEM_SETTINGS_KEY_DEFAULT_FONT_TYPE is not available for setting.
 * @param[in] key The key name of the system settings
 * @param[out] value The new system settings value of the given key
 * @return @c 0 on success, otherwise a negative error value
 * @retval  #SYSTEM_SETTINGS_ERROR_NONE Successful
 * @retval  #SYSTEM_SETTINGS_ERROR_INVALID_PARAMETER Invalid parameter
 * @retval  #SYSTEM_SETTINGS_ERROR_IO_ERROR Internal I/O error
 * @retval  #SYSTEM_SETTINGS_ERROR_PERMISSION_DENIED Permission violation error
 */
int system_settings_set_value_string(system_settings_key_e key, const char *value);