I was googling for a way to have Win7 quickly show me exactly which pic was the current wallpaper on the Desktop. I found this batch file at Stack Exchange.
echo The path to the current Desktop background image is:
REG QUERY "HKCU\Software\Microsoft\Internet Explorer\Desktop\General" /v WallpaperSource
I understand that this method won't work on Win8.x, because the path isn't stored in plain text. Maybe someone else will want a go at that problem.