Most of the images on my website are found and indexed correctly by search engines. However, some of the images are in tags that aren't indexed by Google.

If I create a sitemap for only these types of images, will it negatively affect how google indexes the rest of the site?

Another way of saying this is, if a sitemap is present, does google only index what's in the sitemap or does it continue to crawl all pages, whether they are in the sitemap or not?