Here is the adm file you need for a group policy:
****************************************************
CLASS USER
CATEGORY !!SystemControl
KEYNAME "Control Panel\Colors"
POLICY !!Background
KEYNAME "Control Panel\Colors"
EXPLAIN !!Background_Help
VALUENAME "Background"
PART !!PromptColor EDITTEXT
VALUENAME "Background"
END PART
END POLICY ;Background
END CATEGORY ;SystemControl
CATEGORY !!IconControl
KEYNAME "Software\Microsoft\Windows\Shell\Bags\1\Desktop"
POLICY !!Arrange
EXPLAIN !!Arrange_Help
PART !!PromptArrange DROPDOWNLIST REQUIRED
VALUENAME "FFlags"
ITEMLIST
NAME !!Default VALUE NUMERIC 00000220 DEFAULT
NAME !!ArrangeOn VALUE NUMERIC 00000221
NAME !!ArrangeOff VALUE NUMERIC 00000224
NAME !!ArrangeOnGrid VALUE NUMERIC 00000225
NAME !!Hide VALUE NUMERIC 00001220
END ITEMLIST
END PART
PART !!SortArrange DROPDOWNLIST REQUIRED
VALUENAME "Sort"
ITEMLIST
NAME !!SortName VALUE NUMERIC 00000000 DEFAULT
NAME !!SortSize VALUE NUMERIC 00000001
NAME !!SortType VALUE NUMERIC 00000002
NAME !!SortModified VALUE NUMERIC 00000003
END ITEMLIST
END PART
END POLICY ;Arrange
END CATEGORY ;IconControl
[strings]
SystemControl="Control Panel"
LimitSize="Color of Desktop Background"
Background_Help="Sets the color of the background. 58 110 165 is the default Windows 2000 Color"
PromptColor="Hex Color of Background:"
Background="Windows Desktop Color"
IconControl="Desktop"
Arrange="Desktop Icon Arrangement"
Arrange_Help="Sets the arrangement and placement of the desktop icons"
PromptArrange="How should the icons be arranged?"
Default="Auto Arrange off, Align to Grid off"
ArrangeOn="Auto Arrange on"
ArrangeOff="Auto Arrange off, Align to Grid On "
ArrangeOnGrid="Auto Arange on, Align to Grid on "
Hide="Hide Desktop Icons"
SortArrange="How should the icons be sorted?"
SortName="Sort by name"
SortSize="Sort by size"
SortType="Sort by type"
SortModified="Sort by Modified"
*******************************************