- (IBAction)test:(id)sender
{
 NSDictionary *finderPrefs = [[NSUserDefaults standardUserDefaults] persistentDomainForName:@"com.apple.finder"];
 NSMutableDictionary *finderDict = [finderPrefs mutableCopy];
 NSMutableDictionary *subDict = [[finderDict objectForKey:@"DesktopViewOptions"] mutableCopy];
    [subDict setObject:@"file://localhost/Users/( ... )/whatever.jpg" forKey:@"BackgroundPictureURL"];
    [finderDict setObject:subDict forKey:@"DesktopViewOptions"];
 [[NSUserDefaults standardUserDefaults] setPersistentDomain:[NSDictionary dictionaryWithDictionary:finderDict] forName:@"com.apple.finder"];
  [[NSUserDefaults standardUserDefaults] synchronize];
//find someway to notify the Finder that the defaults have changed
// ...
 [finderDict release];
 [subDict release];
}