I had XAR package with pictures which were imported OK for the first time.
Later on I created a new XAR package with "updated" pictures. I imported it with default option - Add a new version to the existing page. It created a new version, but pictures were not updated (but text from new package was updated OK).
When I wanted to update also pictures, I had to use the second option - Replace the page history with the history from the package.