with a quick search I found a couple plugins you can use to set a video as your wallpaper:

• LivePaper (seems like the better option, but it requires developer mode, so might not work on restricted chromebooks)
• CrosPaper (commercial and not as powerful, but it's in the Chrome Web Store)

I'm guessing that if you want to do these sorts of things and you use Chrome OS, it probably isn't by choice, but get a PC with Windows or Linux if you can. Chrome OS is designed for people that only use their computer to browse the web and don't feel a strong attachment to it; the home for computer customization is really Linux.