With our most recent update (which was yesterday), we have fixed a problem with thumbnails of attached images not showing correctly. (Not always, but sometimes.)
Here’s what the problem used to look like:
As you can see, this card has two images attached. The first one doesn’t show a thumbnail properly (it has a standard “missing image” icon instead) while the second one works fine.
The underlying cause for this was a mismatch in the duration for which Kerika was caching the thumbnail of an attachment after it had first been retrieved from Google Drive, and how long Google Drive was keeping the thumbnail around.
So you never saw the problem when you first attached an image, but if you went back to the card after 30 days you would see the “missing image” icon instead.
We have fixed this. You may still see this if your browser is caching old thumbnails; you can completely eliminate the problem by clearing your browser’s cache, which would force Kerika to request new thumbnails from Google.