Most Viewed Posts Widget With Thumbnails by Blogger

    4.  Set your settings in this way,

  5.   Save your widget and you are done!

May be you will like these widgets too:

• [a href="http://www.mybloggertricks.com/2011/06/related-posts-widget-for-blogger.html" target="_blank"]Related Posts[/a] Widget
• [a href="http://www.mybloggertricks.com/2011/06/recent-comments-widget-by-blogger.html" target="_blank"]Recent Comments[/a] Widget
• [a href="http://www.mybloggertricks.com/2011/06/recent-posts-widget-by-blogger.html" target="_blank"]Recent Posts[/a] Widget

 

For thumbnails to appear make sure you always add an intro image of 100px by 100px at least in your post starting paragraph. The square size will give a more clearer picture. You can make the image as big as 300px by 300px.

Source: http://www.mybloggertricks.com/2011/06/most-viewed-posts-widget-with.html