I've noticed there are two different ways facebook shows an open graph story with an image in a users' feed: one with a small image and the title and description next to it (example), and one with a larger image with the title and description beneath it (example).
Following a tutorial, I was able to generate the large images. However, now that I'm leaving the tutorial and designing my own script, my posts are always shown with the small image.
Anyone has an idea what's causing this? I'm pretty sure both methods use <meta property="og:image" content="someimage.jpg" />
In order to get the large image format your images must be at least 200x200. However, with the new News Feed rolling out soon, you'll want to make your images even larger. Facebook is now recommending 1200x630 images.
Note that even if you are using an image this large, Facebook may still display your story with a smaller image format. Facebook attempts to auto-optimize the format that it shows to people by continually running A/B tests, and so your posts may show up in any of the available image formats.
We recently wrote a blog post showing the different image formats which you may find helpful.
Use an image that is at least 1200 width by 630 height.
Use the Facebook DEBUG tool to call your page again, thereby clearing the Facebook cached version that you uploaded previously at a smaller size:
https://developers.facebook.com/tools/debug/