Ebert,
If I follow, you are trying to force an image to be displayed as the phone wallpaper/background. You have two options:
1. Set the phone background before deploying it and disable user access to phone settings. While it would keep users from changing the wallpaper, it isn't viable because they couldn't change ring tones, screen brightness, etc.
2. Push an image out to the phones and come up with a way to periodically re-push the image. What I am referring to is documented here:
http://www.netcraftsmen.net/resources/blogs/pushbackgroundtoipphone.html
The above link will lay out a method for doing it yourself and I also list a 3rd party application that I have seen others use.
Unfortunately, I am not aware of a policy based solution built into the CUCM or any phone firmware.
HTH.
Regards,
Bill
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