Change wallpaper based on location?

So, just a quick question here. We recently had some new school rules and one of them is any personal devices you bring to school must have a solid grey background, otherwise you will loose computer privileges....don't ask me why, I don't make the rules. So I use my MacBook Pro for notes and projects at school, but I use it a lot more out of school, so I was wondering if there was any way to make it so that when I connect to a certain WiFi network, my wallpaper changes to the default grey one. I am just wondering, because I like to have a nice background but I keep changing it and then changing it back to grey then changing it when I get home..... then more changing. It isn't too much of an inconvenience, but it would be nice if like most things my mac does, it just happens. :)

Sooo... that being said, if there is any program out there that allows you to do this it would be pretty nice. I couldn't find one by quickly doing a google search, but someone might know something ;)

Thanks for any help!