Following are way to clear the facebook's image from cache.
Step 1, Update the Image URL with version in Meta Tags
<meta content="http://www.aboutcity.net/images/web-technology-experts-notes.jpg?v=12" property="og:image"/>
Step 2:
A) Go to https://developers.facebook.com/tools/debug/
B) Enter URL and Press "Debug" Submit button
C) Click On "Show existing scrape information", It will remove the caching
D) Check the updated image
Following is Screenshot which explain, how to clear the Image Cache?