Indexing in Google search engine is very important for a website and website owner. Because it helps to find in search engine result. Doing search engine optimization for website content is important but doing seo for image is also important.
We can do Search Engine Optimization for our web-site content and also for images. To do website image search engine optimization for wordpress, you can use this Google XML Sitemap for Images plugin for wordpress site.
This plugin will help you to create a sitemap in .xml for your images. And after creating sitemap for images you can submit this image sitemap to Google using Google webmaster tool.