It's standard practice to tell the users of your product something so simple, launch arguments are built into nearly every program for windows, all with clear documentation.
I just want to do this project and I didn't want to pay for Wallpaper Engine, which I could do if someone could just tell me how I can make the program load a wallpaper in a way that I can interface with.
I don't think you quite understand what I'm trying to accomplish here.