Problem Solved!

The correct path to the images is:

multisites/slave1/images/mypicture.jpg


Mike

When you are using this path, this mean that you have used the {rel_site_dir}/images and therefore that your slave site is defined in your hosting server as having the same directory than your master website (case of Windows or Unix that does not deployed slave site into a specific directoy).

So this is also correct when the hosting server is assigned to the master website directory.
This is another scenario than the one presented in the video reference in our previous reply.