Question:
How do I change the Windows wallpaper in code?
Answer:
Call the Windows API function SystemParametersInfo()
passing the SPI_SETDESKWALLPAPER parameter along with
the filename of the new bitmap to use.
Example:
SystemParametersInfo(SPI_SETDESKWALLPAPER,
0,
PChar('C:\SOMEPATH\SOME.BMP'),
SPIF_SENDWININICHANGE);