リンクをシェア、ライクした時の ニュースフィードでのOGP画像の表示領域が若干大きくなりましたよっと開発者ブログからメルマガが来ました。
英語弱いので違うかもだけど。あしからず。

Showing larger images for links in news feed
Now, when a person shares a link to a page in your app that contains a large image (200x200px or larger), it will be presented more prominently in news feed. These larger images draw higher engagement from friends, which drives more people to your app.
To take advantage of this improvement, be sure to include large images and tag them appropriately. Please provide the largest images you have, and we will automatically downsample and crop them for people based on the device they’re using. For more information, please see

our documentation
https://developers.facebook.com/docs/opengraphprotocol/

and
best practices
https://developers.facebook.com/docs/technical-guides/opengraph/maximizing-distribution-media-content/
.

というわけでリンクはって投稿してみたところ、若干大きくなっている模様。156*156pxだっけな。

ふう～ん。