This tweet renders as a photo card correctly: https://twitter.com/dblocktest/status/246447500783923200
This one does not: https://twitter.com/dblocktest/status/246446354413518849 (renders as a summary with the correct thumbnail)
First image is art.sy/artwork/peter-alexander-6-slash-1-slash-12-blue-square
Second image is http://art.sy/artwork/peter-alexander-untitled
I read the docs twice and I can’t find a reason why this happens. Is it because the first image is Twitter blue?