A solução simples é substituir o plano de fundo padrão do Windows, caso o serviço Temas esteja em execução e o Aero esteja habilitado, localizado aqui:
C:\Windows\Web\Wallpaper\Windows\img0.jpg
O que eu venho fazendo há algum tempo por um projeto de VDI foi ativar o serviço Themes e o Aero na imagem da VM e adicionar o seguinte registro ao usuário padrão (observe que estou usando uma imagem personalizada como plano de fundo ). Certamente recomendo testá-lo em um laboratório primeiro:
[HKEY_USERS\.DEFAULT\Control Panel\Cursors]
@="Windows Aero"
"Scheme Source"=dword:00000002
[HKEY_USERS\.DEFAULT\Control Panel\Desktop]
"UserPreferencesMask"=hex:90,12,03,80,10,00,00,00
"WallPaper"=hex(2):43,00,3a,00,5c,00,55,00,73,00,65,00,72,00,73,00,5c,00,25,00,\
55,00,53,00,45,00,52,00,4e,00,41,00,4d,00,45,00,25,00,5c,00,41,00,70,00,70,\
00,44,00,61,00,74,00,61,00,5c,00,52,00,6f,00,61,00,6d,00,69,00,6e,00,67,00,\
5c,00,4d,00,69,00,63,00,72,00,6f,00,73,00,6f,00,66,00,74,00,5c,00,57,00,69,\
00,6e,00,64,00,6f,00,77,00,73,00,5c,00,54,00,68,00,65,00,6d,00,65,00,73,00,\
5c,00,54,00,72,00,61,00,6e,00,73,00,63,00,6f,00,64,00,65,00,64,00,57,00,61,\
00,6c,00,6c,00,70,00,61,00,70,00,65,00,72,00,2e,00,6a,00,70,00,67,00,00,00
[HKEY_USERS\.DEFAULT\Control Panel\Desktop\WindowMetrics]
"BorderWidth"="-15"
"CaptionFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"CaptionHeight"="-315"
"CaptionWidth"="-315"
"IconFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\
00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"IconTitleWrap"="1"
"MenuFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,00,\
00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"MenuHeight"="-285"
"MenuWidth"="-285"
"MessageFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"ScrollHeight"="-255"
"ScrollWidth"="-255"
"SmCaptionFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,\
00,00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"SmCaptionHeight"="-255"
"SmCaptionWidth"="-255"
"StatusFont"=hex:f4,ff,ff,ff,00,00,00,00,00,00,00,00,00,00,00,00,90,01,00,00,\
00,00,00,01,00,00,05,00,53,00,65,00,67,00,6f,00,65,00,20,00,55,00,49,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"Shell Icon Size"="32"
"AppliedDPI"=dword:00000060
"PaddedBorderWidth"="-60"
"IconSpacing"="-1125"
"IconVerticalSpacing"="-1125"
"MinAnimate"="0"
[HKEY_USERS\.DEFAULT\Software\Microsoft\Internet Explorer\Desktop\General]
"WallpaperSource"="C:\WINDOWS\web\wallpaper\Windows\img0-win7.jpg"
[HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Explorer\Wallpapers\Images]
"ID-1"="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"
[HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\ThemeManager]
"ThemeActive"="1"
"LoadedBefore"="1"
"LastUserLangID"="1033"
"LastLoadedDPI"="96"
"DllName"=hex(2):25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,\
74,00,25,00,5c,00,72,00,65,00,73,00,6f,00,75,00,72,00,63,00,65,00,73,00,5c,\
00,54,00,68,00,65,00,6d,00,65,00,73,00,5c,00,41,00,65,00,72,00,6f,00,5c,00,\
41,00,65,00,72,00,6f,00,2e,00,6d,00,73,00,73,00,74,00,79,00,6c,00,65,00,73,\
00,00,00
"ColorName"="NormalColor"
"SizeName"="NormalSize"
[HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Themes]
"CurrentTheme"="C:\WINDOWS\resources\Themes\aero.theme"
[HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\DWM]
"Composition"=dword:00000001
"ColorizationOpaqueBlend"=dword:00000000
"EnableAeroPeek"=dword:00000000
"AlwaysHibernateThumbnails"=dword:00000000
"CompositionPolicy"=dword:00000002
"ColorizationColor"=dword:6b74b8fc
"ColorizationColorBalance"=dword:00000008
"ColorizationAfterglow"=dword:6b74b8fc
"ColorizationAfterglowBalance"=dword:0000002b
"ColorizationBlurBalance"=dword:00000031
"ColorizationGlassReflectionIntensity"=dword:00000000