Force Desktop picture for local users

Hello,

I have a bunch of clients under an Open Directory, managed with WorkGroup Manager. I need to enforce the use of a specific image for my local machines users.I’ve found under preferences -> Details a Desktop Picture voice editable with some values for a plist. So I’ve tried to specify a path with a record creation called ImageFilePath, string as type and as value my image’s full path, but this doesn’t help.

Anybody can help me?

thanks in advance