1. Login to Blogger.
2. Go to Dashboard >> write new post (or edit posts).
3. Add the image using the default tool of Blogger.
4. Click "Edit HTML", near "Compose".
5. Find these codes, delete the bold part
<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="http://somewhere-in-blogger/your-image.jpg">
<img style="margin: 0pt 10px 10px 0pt; float: left; cursor: pointer; width: 75px; height: 75px;" src="http://somewhere-in-blogger/your-image.jpg" alt="" id="BLOGGER_PHOTO_ID_some-number-here" border="0">
</a>
6. Publish post, and done.
Your images will not be click-able any longer and won't serve as click-to-enlarge links. Feel free to use comment box if you have any question or comment :D