My (in no way SEO professional) take on this 8 years later using the information from Google employees that has popped up in the meantime.
From my experience, this is what most plugins and extensions will generate for you. So running each Sitemap Protocol-defined tag through the process of elimination:
You actually need to re-authenticate your new www site. www is a subdomain, and unless your registered a domain with all it's subdomains to Google Search Console, you need to register every subdomain. Since you need open a new asset in Google Search Console, you will also need to resubmit your sitemap.xml
Thanks to the comment from Stephen, I am adding a ...
Google image search has people click through to the page containing the image, not the image itself. It needs an index-able landing page containing the image to index the image. There is no way to have Google image search index an image without using it on a page that can be indexed.
You have three options:
Decide not to have this image indexed.
Make the ...