WordPress for free users is very, very limited. You don’t have the ability to add on extras or edit the source code to make it see properly the thumbnail you wish to have set. It’s most annoying because Facebook often takes things unrelated to your WordPress entry as the thumbnail. Even if you have an image in your article the right size for Facebook, it still goes ignored.
I did a lot of research and kept coming across the paid version of WordPress users how to set your default thumbnail. As useful as that is, not everyone has the paid version of WordPress. In fact very few of my friends do. So I know I’m not alone when seeking the answer to this most annoying problem. And hopefully I can help you out.
I felt I was getting no where fast with my research to this thumbnail problem. I edited images I had linked in the hopes the Facebook Debugger http://developers.facebook.com/tools/debug/ Would do the trick and pick up the right image. No luck, everything but what I wanted as my WordPress thumbnail was coming up! Talk about annoying.
Nearly at the end of my rope with WordPress and attempting to face the disappointment of never having a default thumbnail of my choice I started poking around in my own WordPress Dashboard seeking somehow to change this option. I clicked on settings at the bottom left. And found “Blog Picture / Icon” I thought to myself, could this be the default thumbnail I’ve been looking for? Could it really be this easy?! Sure enough it was!
So that’s the answer, really that simple, yes? You can set your default thumbnail in the free version of WordPress by going to Settings, and changing your Blog Picture /Icon to whatever you want! They will allow you to crop it as you see fit. Remember thumbnails are of equal height. So make it 200 by 200 or 150 by 150. I wouldn’t recommend going any smaller for your thumbnail.
After you have changed your default thumbnail in WordPress be sure to toss your blog link in the Facebook Debugger so it can update across the board. This should remove the cache issue with the other images. This will now ensure when others share your WordPress latest entry, it’s shared with the thumbnail you wouldn’t mind! I find selecting your banner image is best. This way others know its you right away by your thumbnail.
I figured this out myself, because as I shared above, nothing was on the internet about the FREE version of WordPress, only the paid version. If you have the free version of WordPress and this works for you, please let me know how useful this was for you.