Its works  for Xp user only

Copy this code to ur text editor,then save it as "desktop.ini"
 

Code:

[.ShellClassInfo]
IconFile=%SystemRoot%\system32\SHELL32.dll
IconIndex=127
ConfirmFileOp=0

[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
Attributes=1
IconArea_Image="your_picture.jpg"
IconArea_Text="0xFFFFFF"

VeBRA sources - don't delete the tag above, it's there for XXXXX purposes -
[ExtShellFolderViews]
{BE098140-A513-11D0-A3A4-00C04FD706EC}={BE098140-A513-11D0-A3A4-00C04FD706EC}
{5984FFE0-28D4-11CF-AE66-08002B2E1262}={5984FFE0-28D4-11CF-AE66-08002B2E1262}

[{5984FFE0-28D4-11CF-AE66-08002B2E1262}]
PersistMoniker=Folder.htt
PersistMonikerPreview=%WebDir%\folder.bmp

__________________________________________________ __________________________________________________ __
(Note in :IconArea_Image="your_picture.jpg" enter the name of your picture.)

2.Put "desktop.ini and your_picture.jpg in ur USB Drive then Hidden it.
3.Refresh ..and enjoy with new background.....