Hi, no you have to use a third party (native) app. Maybe there is an executable in Windows or Mac to do that.
Command line to do that from Windows:
reg add "HKCU\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d "C:\mon_image.bmp" /f
I'll check into using native apps. I like the idea of targeting both Windows and Mac and this idea could do both.