I'm also seeing the same issue with the size of the image previews in 10.86.5 Evernote on Mac. The preview image used to fill the bottom of the card completely which looked amazing, and now it is just a boring small square. I'm also noticing many of my recent image uploads are coming in as a 'blank' file image in the preview but shows up correctly in the note itself. I am hoping they will address these issues soon. As a visual person, the small images don't feel or look as good as they used to.