I'm keen to get an image sitemap or include my images in the XML sitemap of my site. I updated NextGen Gallery and downloaded Yoast WordPress SEO, as they are supposed to work together. However, ticking "Add images to XML Sitemap" in the Yoast WordPress SEO settings and then viewing the sitemap shows no images.
This is a sample of the sitemap that's generated
Other plugins that are supposed to generate image sitemaps don't work either. I don't have anything restricted on robots.txt and only a few images are indexed by Google.
Could anything be stopping images being picked up by image sitemap makers? Any other suggestions?