I'm unable to get Easy Fancy Box to work on all existing images in my blog. I've gone though the help to verify that all is working. There is one area of concern which is the following paragraph written on Easy FancyBox page;
# Make sure that thumbnail images are linked directly to their larger counterpart, not to a dynamic WordPress page that includes the larger image. This means when you insert an image in your posts or pages, you need to select File URL at the Link option instead of Page URL. You’ll have to manually edit your old posts if you have always inserted images with Page URL before, FancyBox cannot do this for you.
I use Link URL, here is a link to a older digital painting post I had posted demonstrating that Easy FancyBox is not working.