Active idle theme cannot be changed by 3rd party applications (Known Issue)
The S60 active idle standby theme cannot be changed by 3rd party applications programmatically from S60 3rd Edition, FP2 onwards. Only the Themes application can get and set the list of installed active idle plug-ins. Security in using these services is guaranteed by controlling the rights to the theme server, and third-party applications cannot access this server.
No solution available. The user has to manually change the active idle theme from the Themes settings.