IceWM Service Pack 3:
I believe this is the most accurate Windows XP/Luna theme for IceWM in existence as of now.
Not much to say; this was heavily based on "1 in 1 XP" by Adisk (in particular, it has his window borders and buttons). The theme file is smaller and cleaner than 1 in 1 XP and many of the other pixmaps are taken direct from screenshots of Windows XP.
As might be expected, this cannot be licensed under GPL or any other F/OSS license as it uses pixmaps from a copyrighted work.