change desktop wallpaper via command line

reg add "hkcu\control panel\desktop" /v wallpaper /t REG_SZ /d "C:\path\wallppr.bmp" /f
then apply the settings,
RUNDLL32.EXE user32.dll,UpdatePerUserSystemParameters



convert jpg / png to bmp , because jpg / png wont refresh via command line by user32.dll
djpeg -bmp -outfile 1.bmp .\filein.jpg
png2bmp -O 1.bmp -Q .\filein.png