If you optimize a JPEG image, it can go from from 1.4MB to 10KB. By optimizing the images you can also reduce loading time of images substantially. Below I mentioned 15+ Tips To Optimize Images For Search Engines.
MUST CHECK : 20+ Tools To Optimize Images For Search Engines
1. WordPress Plugin : You can try SEO Friendly Images, a WordPress plugin, for optimizing images on your WordPress Blog. It will automatically optimize image ALT and TITLE tags.
2. Title and Alt : Alt attribute is very essential for optimizing Images for search engines. You have to describe the image in short.
3. Resize : Always resize the images using a software (like Photoshop) or any other online tools. Don’t use HTML or CSS properties to do it.
4. Robots.txt File : Your robots.txt should permit search engines to read the images folder. The images folder should not be blocked by your robots.txt file.
5. File Name : Always use relevant file name. If you have a ball picture, the file name should be “ball”. If it is a red color ball, then the file name should be “Red Ball”. Use hyphens (-) instead of underscores ( _ ). Simple enough right? 
6. Use Captions : Place a small caption near to the image. Let it be at the top or bottom, right or left. Caption should be relevant to the image.
7. Be Relevant : The image should match the content and vice versa. Images can compel the visitors and readers to stay longer.
8. Enable Image Search : Make sure you have enabled Image Search on Google Webmaster Tools. If you have not, do it now!
9. Save For Web : Always use Adobe Photoshop to optimize your images. For better optimization try Save for the Web feature. Go to File | Save For The Web. By this you can optimize images to desired size and quality. You can also try Adobe Fireworks.
10. No Bitmaps : Avoid Bitmaps since it is not very good in Search Engine Image Optimization. Try other common and famous formats instead. See 13th Tip.
11. Useful Tools : You can use this online image optimizer from Dynamic Drive. You can check this list of useful tools for optimizing images.
12. Crop : Leave the essential parts of the images and crop the rest. It will also help you take up less space on your page. Usually, people will crop the white space around the images.
13. Right Format : These are the commonly used Image Formats.
JPEG – For Photos
GIF – For Animations
PNG – For Logos, Icons, Buttons and so on.
14. High Quality Images : It is believed that people pay more attention to clear images where they can see details. So always use High Quality Images. Avoid Blur and Abstract images. You can check the list of sites providing high quality images here.
15. Images Per Page : Try to avoid many images on a single page. Limited number of images per page is good for optimizing images for search engines.
16. Optimized Hosting : Popular image hosting site, Flickr is believed to help Yahoo! image optimization. So chose Popular and reliable photo sharing hosting, if you are not using WordPress! 
17. New Location : Generally, the default location of Images is not good in terms of Image Optimization. You can change the default location of images on WordPress, by creating a new sub domain and shifting the Images Folder.
18. Original Images : Experts believe that it is good in terms of Image Optimization to use original images. You can brand the images through Watermarks or logos.
If you know any other good tip for optimizing Images for search engines, please share it in the comments!