I´m having the same doubt but I´m using thumbnails, don´t sure if this plugin works with the images outside of the content.

Any help is welcome 🙂

Plugin not working for thumbnails(also main page) and side bar images. Working in just post pages.

http://wordpress.org/extend/plugins/bj-lazy-load/
and
http://wordpress.org/extend/plugins/jquery-image-lazy-loading/

I have tried both but that was some compatibility problems with my other plugins (Releated post&Social Media Tabs).