Well, I found the answer on my own. Just putting here in hope it will help someone coming here.
The images in blog enlarged after clicking, and displayed one by one is done by Blogger's Lightbox feature. We can customize the enlarged images (e.g. we can make them round cornered, put shadow to them etc.) by doing this:
Go in bloggers HTML editor of template
Search using CTRL + F the tag < /head> (No space between '<' and '/')
Just above the tag, add the following code:
<style> .CSS_LIGHTBOX_SCALED_IMAGE_IMG { outline: 0px solid #fff !important; -webkit-border-radius: 10px; -moz-border-radius: 10px; border-radius: 11px; -webkit-box-shadow: 0px 0px 5px #000000; -moz-box-shadow: 0px 0px 5px #000000; box-shadow: 3px 3px 7px #888; } </style>
For more details please refer this:
http://helplogger.blogspot.in/2013/03/how-to-customize-bloggers-lightbox.html