Modify the per-user picture folders suggested in "Desktop & Screen Savers"

picture_folders.py

from CoreFoundation import CFPreferencesCopyAppValue, CFPreferencesSetAppValue, CFPropertyListCreateDeepCopy, kCFPropertyListMutableContainersAndLeaves, CFPreferencesAppSynchronize

folder_to_add = u'/Abosulte/Path/To/Folder'

desktop_settings = CFPreferencesCopyAppValue('DSKDesktopPrefPane', 'com.apple.systempreferences') or dict()

mutable_desktop_settings = CFPropertyListCreateDeepCopy(None, desktop_settings, kCFPropertyListMutableContainersAndLeaves)

folder_paths = mutable_desktop_settings.get('UserFolderPaths', list())

if folder_to_add not in folder_paths:
    folder_paths.append(folder_to_add)

mutable_desktop_settings['UserFolderPaths'] = folder_paths

result = CFPreferencesSetAppValue('DSKDesktopPrefPane', mutable_desktop_settings, 'com.apple.systempreferences')

result = CFPreferencesAppSynchronize('com.apple.systempreferences')