Comment 11 for bug 510212

One problem I see of using an Ubuntu-branded icon instead of the usual brown box is that it uses the "update-manager" icon in the gtk icon cache. So, depending on what icon theme a user uses (eg, the Ubuntu default or Faenza or whatever), the image on the main window will change. The only way to avoid that would be to hard-code an image, which is usually not a good idea, uniformity-wise.