Question

Is there a way to change the Windows wallpaper using some new feature in .NET 4?

Answer 1

You can use SystemParametersInfo to set the desktop wallpaper. This should work consistently on all versions of windows that your app can run on, however will require some interop.

The following interop declarations are what you need

public const int SPI_SETDESKWALLPAPER = 20;
public const int SPIF_UPDATEINIFILE = 1;
public const int SPIF_SENDCHANGE = 2;

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern int SystemParametersInfo(
  int uAction, int uParam, string lpvParam, int fuWinIni);

Which can be used like this to change the desktop wallpaper

SystemParametersInfo(
  SPI_SETDESKWALLPAPER, 0, "filename.bmp", 
  SPIF_UPDATEINIFILE | SPIF_SENDCHANGE);