Thanks for the inspiration, this will be my new project.
Basically the server host will upload their 1024x768 image to a site (I will be creating) which will be reviewed and accepted/rejected. The host sets the given image ID via an RTB pref (slash command too, I suppose).
I'm keeping the site idea, but I think i'm going to have a report feature instead of an approval system.
When the client connects, it sends the ID to them, while the client downloads the image and displays it on the loading screen (if the image is accepted).