When my Client searches with keywords at Google no images of the example.com website show in SERPs. We gave alt text for every images but didn't get any results.
Now, I need to know that is there any importance to add a image sitemap for better search results?
What I can tell you for certain, is that adding an image sitemap into your webmaster account, allows you to tracking the index status of your images.
For example, lets say I have some 10 odd pages on my site, each with 2-3 images on them. That's around 30 images overall linked to the actual pages. However, when I was uploading those images, I uploaded 50+ images. Clearly, some of these images are not linked on the visible site.
What an image sitemap will allow you to do is give you a simple status such as 20 images out of your 50 images have been indexed. This should address your question.
Try re-sharing the images on social networks. On twitter, on Google plus too. Also, make sure the image titles are relevant and descriptive of the images themselves. Replace generic names like "image1.jpg"
