Is there any way to set Wallch to rotate through different wallpapers on different monitors, using Twinview? I'm assuming the same trick for workspaces doesn't work for monitors. Thanks
At the time of writing, no, there isn't. Whether or not you're using Twinview doesn't come into it.
I found something for you. It doesn't use Twinview or Wallch. :) Here, take a look: http://ubuntuguide.net/ubuntu-11-04-unity-enable-different-wallpapers-in-each-workspaces
Ps.: If my answer was useful, please rate. :)