Hi @blazejewicz, thanks for starting a new thread.
There is an error that is not being surfaced in your case. There are a couple of issues. Twitter is looking for an image and is falling back on the og:image. That’s ok, however the URL in og:image is not an absolute URL.
Even when I do construct a URL for your image there is no image at:
http://marionettejs.com/images/marionette_logo.png
Additional the Twitter bot will look for a robots.txt where your image is hosted, so you will need one at:
http://marionettejs.com/robots.txt
Btw, love the project. I’m a long time backbone.js user.