@webdeersign yes this is how i do it as well, works great but I have a small tip,
Just create a page IN your project called, og.html
in this page you import your FB or Twitter pics.
So design a picture for FB,
Save it in your assets folder,
Import it in your project,
en then in your og.html page you just insert the picture.
why? because now this og.html page belong to your project, and every time you export and upload your complete project it to your server, the FB picture is in the standart img folder of your Blocks project as well, and you never forget it ( I had that a few times )
so it will be: