Yes, I was able to do it, but to replace a single icon for both states of the device.
But I saw at this post that is possible to adapt the CSS to display different icons per device states. I really tried to implement it, but wasn't able to make it work, I just messed the CSS - happily I made a security copy before trying...
The solution used there points to an image externally hosted, but I think that would be easier to use a locally stored image.
